U.S. Secretary of State Hillary Rodham Clinton pressed some of the world's last remaining friends of Moammar Gadhafi to abandon Libya's strongman and join the growing international demand for him to cede power. She told African nations that their solidarity with the Libyan people could make the difference for a peaceful future.

Culminating a volcano-shortened trip to the Gulf and three African nations, Clinton told diplomats at the African Union headquarters in Ethiopia's capital that they needed to recognize that Gadhafi forfeited his legitimacy to rule by attacking his own citizens.

It represented a difficult call for unity. Gadhafi still has many friends in Africa after providing decades of military training and patronage for groups fighting apartheid and colonialism.

"Your words and actions could make the difference in bringing this situation to a close and allowing the people of Libya to get to work rebuilding their country," Clinton told African officials in Addis Ababa. She said the world needed African leadership to end the standoff between opposition forces and Gadhafi's troops.

For Clinton, the emphasis on the Libyan leader provided a full circle for a one-week voyage that began in the United Arab Emirates, where she prodded NATO countries and Arab governments participating in the U.N.-mandated military mission against Gadhafi to increase the pressure on him to leave power and increase their contacts with the Transitional National Council.

After stops in Zambia and Tanzania, she was to have spent Monday night in Addis Ababa. But she was forced to leave the Ethiopian capital a day ahead of schedule when a volcano eruption in nearby Eritrea sent an ash cloud over parts of East Africa. Officials said the airport in Ethiopia's capital was to be closed, and Clinton faced being stranded if she had proceeded with her planned events.

Although Clinton departed earlier than planned, she should not arrive in Washington ahead of her scheduled Wednesday arrival time because she'll have a long layover in Europe.

The timing of Clinton's return is being closely watched because her traveling party includes senior aide Huma Abedin. Abedin is the wife of embattled New York Rep. Anthony Weiner, who is facing calls to resign because of sexually-charged messages and photos he sent to several women online. Weiner reportedly wants to speak with his wife before making a decision on stepping down.

In Ethiopia, Clinton acknowledged that Gadhafi's "major role in providing financial support for many African nations and institutions, including the African Union." But she said it has become clear in light of his abuses that he cannot remain in power.

All African leaders should demand that Gadhafi accept a ceasefire and then leave Libya, she said. They should expel pro-Gadhafi Libyan diplomats from their countries, suspend the operations of Libyan embassies and work with the Libyan opposition.

Since seizing power in Libya in 1969, Gadhafi has offered training, funding and other support for African rebel groups, including the African National Congress as it fought white minority rule in South Africa. Buoyed by oil money, he also paid the membership dues of many smaller, poorer countries at the United Nations, African Union and other international bodies _ winning himself a cast of supporters even as he fancied himself the continent's "king of kings."

While the Arab Leagues suspended Libya's membership in the midst of the crisis, Gadhafi is still seen as a hero by many African leaders. His government remains a member in good standing in the African Union. Among the scenarios that Western nations have debated to resolve the situation include Gadhafi's possible exile to a friendly African country.

The revolt against Gadhafi in Libya is just one among many in the Middle East and North Africa. The longtime leaders of Tunisia and Egypt have been ousted and anti-government protests have faced severe crackdowns in Bahrain, Syria and Yemen.

Clinton said that repressive governance is no longer accepted in the world. She said discontent, mainly among exploding youth populations in Africa, the Middle East and elsewhere cannot be suppressed in the era of the internet and social media.

"Too many people in Africa still live under long-standing rulers _ men who care too much about the longevity of their reign and too little about the legacy that should be built for their countries' future. Some even claim to believe in democracy defined as one election, one time," she said to laughter.

Clinton said that approach has been soundly rejected, noting the Arab uprisings.

"After years of living under dictatorships, people have demanded new leadership in places where their voices have long been silenced," she said. "They are exercising their right to speak at the top of their lungs."

African governments, too, must enact broad social, economic and political reforms or they will face similar revolts, Clinton said.

In Addis Ababa, Clinton also met separately with officials from Sudan's northern and southern governments and helped advance the U.S. goal of an Ethiopian peacekeeping force being sent to the disputed, oil-rich region of Abyei. The two sides agreed in principle Monday to demilitarize the region, after two days of talks between Southern Sudan President Salva Kiir and Sudan President Omar al-Bashir aimed at defusing threats of a renewed military conflict.

Both sides claim Abyei, but the north sent troops into the region last month. Tens of thousands of residents fled to the south, which will become the world's newest independent country on July 9. The north and the south fought a debilitating two-decade civil war that ended in 2005.

"I was hoping to spend a long time talking to you but I am being chased by a volcano," Clinton told Kiir.

Clinton's travels have often been dogged by natural disasters. She arrived in Tanzania on Saturday, a day after the capital Dar es Salaam was shaken by a small quake.

Clinton told officials that she would return to Ethiopia and finish her itinerary when her schedule permits, State Department spokesman Mark Toner said in Washington. She had planned to visit a women's health center and see a demonstration of clean cook stoves aimed at preventing deaths from smoke inhalation among poor African communities.

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Associated Press writer Bradley Klapper in Washington contributed to this report.