HAVANA (AP) — The Latest on President Barack Obama's trip to Cuba (all times local):

3:40 p.m.

Cubans are expressing shock at seeing President Raul Castro answer questions from reporters, a rare occurrence that was broadcast live on state TV.

Especially interesting were questions for Castro about human rights and political prisoners.

"It's very significant to hear this from our president, for him to recognize that not all human rights are respected in Cuba," said Raul Rios, a 47-year-old driver. Rios says he agrees with the Castro's argument that no country is perfect and all should strive to do better.

Marlene Pino, an engineer, also 47, says: "This is pure history and I never thought I'd see something like this. It's difficult to quickly assimilate what's happening here. For me it's extraordinary to see this."

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3:10 p.m.

Cuban President Raul Castro is pushing back against President Barack Obama's call for greater human rights and democracy in Cuba.

Castro restated his government's long-stated position that it simply places different emphasis on a wide range of human rights, assuring its people free health care and education while restricting activities by people it considers to be U.S. agents acting to destabilize the government.

Castro said no country meets all international standards on human rights.

Castro spoke at a news conference with Obama — a highly unusual event in the communist country. The session was broadcast live on Cuban state television. Cubans interviewed on the streets said they were shocked at seeing Castro being challenged by reporters.

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3:05 p.m.

President Obama says he believes the Cuban trade embargo is going to end, and while he can't predict when that will be, he believes it will happen at some point because the embargo has not served the interest of the U.S. or the Cuban people.

Obama says the U.S. has exercised as much flexibility as it can to make modifications to the embargo, but the list of things his administration can do is growing shorter.

The bulk of changes will rely on Congress. He said that while Congress is not as productive as he would like during elections years, the large number of lawmakers making the trip to Cuba shows a growing interest in lifting the embargo.

Obama says that how quickly that Congress ends the embargo also will likely depend on how Cuba addresses concerns about human rights.

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2:40 p.m.

The leaders' press conference has resulted in an extraordinary interchange between CNN reporter Jim Acosta, a second-generation Cuban-American, and Raul Castro, a figure of absolute authority in Cuba who is never subjected to aggressive questioning by the state-controlled press or exposed to questions from independent foreign reporters.

When asked why Cuba has political prisoners, Castro testily addressed Acosta directly, saying "Give me the list now of political prisoners to release ... if there are political prisoners they'll be free before nightfall."

Cuba is criticized for briefly detaining demonstrators thousands of times a year but has drastically reduced its practice of handing down long prison sentences for crimes human rights groups consider to be political. Cuba released dozens of political prisoners as part of its deal to normalize relations with Cuba and Amnesty International said in its 2015/2016 report that it knew of no prisoners of conscience in Cuba.

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2:30 p.m.

President Barack Obama says he and Cuban President Raul Castro had a "frank and candid conversation" on human rights and democracy, and are making progress in tearing down barriers between the two nations.

In extended remarks after the first private meeting between the leaders, Obama declared it a "new day" in relations between the U.S. and Cuba.

The president noted the two nations have "very serious differences," particularly on areas regarding freedom of speech, assembly and religious liberty. But Obama says he believes the two governments are capable of having a "constructive dialogue."

Obama noted success in increasing travel between the nations, increased trade and tourism. He says he's working to ease the path for joint corporate ventures and hiring more Cubans in the U.S.

Obama sought to reassure Cubans wary of the return of U.S. engagement. He says: "Cuba's destiny will not be decided by the United States or any other nation. ... The future of Cuba will be decided by Cubans not by anybody else."

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2:10 p.m.

Cuban President Raul Castro is calling on President Barack Obama to lift even more restrictions on Cuba.

He's also urging the return of land used for the U.S. naval base at Guantanamo Bay.

Castro says in a statement after Monday's meeting with the U.S. president that he welcomes changes by Obama to allow commercial flights to resume and changes in the area of telecommunications, for example. But he says an economic blockade that remains in place is the "most important obstacle" to Cuba's economic development and the well-being of the Cuban people.

Castro says he recognizes that Obama wants the blockade lifted entirely, but that Congress has refused to go along.

Castro spoke after meeting with Obama in Havana during Obama's historic visit to the island nation.

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1 p.m.

Google is opening a cutting-edge online technology center at the studio of one of Cuba's most famous artists, offering free Internet at speeds nearly 70 times faster than currently available to the Cuban public.

President Barack Obama says Google's effort is part of a wider plan to improve Internet access across the island.

The U.S. technology giant has built a studio outfitted with laptops, cellphones and virtual-reality goggles at the complex run by Alexis Leiva Machado, a sculptor known as Kcho.

In an exclusive tour of the site for The Associated Press on Monday, Brett Perlmutter, Google's head of Cuba operations, said the company was optimistic that the studio would be part of a broader cooperative effort to bring Internet access to the Cuban people.

The project has limited reach but enormous symbolic importance in a country that tightly controls of Internet access. Some Cuban officials see the Internet as a potential tool for the U.S. to exert influence over the island's culture and politics.

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12:15 p.m.

Western Union is joining the growing list of companies looking to conduct more business in Cuba.

The company says it intends to expand its service handling money transfers to Cuba in response to new regulations announced last week by the Obama administration.

Western Union already handles remittances from the United States to Cuba. Soon, it will begin processing remittances from other countries into Cuba.

Monday's statement from Western Union quotes company executive Odilon Almeida as saying remittances to Cuba fund families and private small businesses and can be a "powerful catalyst for empowerment and innovation."

A key goal of Obama's regulatory changes is to support the island's 400,000 or so private entrepreneurs, who have been allowed to go into business for themselves under economic reforms instituted by President Raul Castro.

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11:45 a.m.

Agriculture Secretary Tom Vilsack has announced that the United States and Cuba will share agricultural research and ideas, a move designed to help U.S. farmers better understand the Cuban market.

U.S. farmers are eager to step up access to Cuban markets. Agricultural exports to Cuba have fallen to their lowest levels since 2002, making the U.S. Cuba's fourth-largest supplier behind the European Union, Brazil and Argentina.

Vilsack is in Cuba as part of President Barack Obama's visit to the island. Vilsack has signed a memorandum of understanding with Cuba's agricultural minister establishing how the two nations will share research.

The various activities researchers will undertake include testing recipes and specific products used by Cubans with the goal of increasing product development and acceptance. They will also study students' eating practices to help ensure they're getting adequate nutrition.

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11 a.m.

President Barack Obama has signed many guest books during his time in office, but the message he left behind for Cubans is one for the history books.

"It is a great honor to pay tribute to Jose Marti, who gave his life for independence of his homeland. His passion for liberty, freedom, and self-determination lives on in the Cuban people today," Obama wrote in dark ink in the book after he laid a wreath and toured a memorial dedicated to the memory of Jose Marti.

Marti was an influential poet and journalist who became a symbol for Cuba's bid for independence against Spain in the 19th century.

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10:45 a.m.

In a long-anticipated moment, President Barack Obama and Cuban President Raul Castro shook hands warmly and smiled for the cameras as they greeted each other at the Revolutionary Palace.

It was the leaders' first meeting since Obama arrived in Cuba on Sunday and a milestone in the new era of closer relations between the two countries.

Obama and Castro exchanged words briefly, although their remarks were not picked up by the television cameras nearby.

The men then watched a display of Cuban troops. Secretary of State John Kerry, National Security Adviser Susan Rice and several other U.S. officials looked on.

Obama and Castro have met before. They first shook hands in 2013 in South Africa at the Nelson Mandela's funeral.

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10:30 a.m.

President Barack Obama's first stop on his first full day in Cuba was Revolutionary Square, home to a memorial to Cuba independence hero Jose Marti.

Obama arrived midmorning for a brief wreath-laying ceremony. Standing in a lineup of Cuba and U.S. officials, the president listened as a military band played both the Cuban and American national anthem. He held his hand on his heart for the "Star Spangled Banner" and watched as three Cuban soldiers carried a massive wreath of red and white roses to the base of the Marti memorial. Obama made no remarks.

The scene was heavy with reminders of Cuba's history.

Behind Obama were striking steel sculptures of two Cuban Revolution figures: Ernesto "Che" Guevara and Camilo Cienfuegos.