UNITED NATIONS (AP) — U.N. Secretary-General Antonio Guterres will open the signing ceremony for the first treaty to ban nuclear weapons and the Security Council hold a high-level meeting on its far-flung peacekeeping operations as world leaders tackle a wide range of crises and challenges on the second day of their annual gathering.

More than 120 countries approved the treaty in early July over strong opposition from nuclear-armed countries and their allies, who boycotted negotiations. The U.N. treaty office said 51 countries are expected to sign during Wednesday's opening day.

Guterres is also expected to brief the Security Council meeting on reforming U.N. peacekeeping — a key item on the Trump administration's agenda, which will be represented by Vice President Mike Pence.

Ethiopia's U.N. Mission, which holds the council presidency, said nine presidents, three vice presidents, six prime ministers, three deputy prime ministers and more than 30 foreign ministers are scheduled to attend the day-long session where 71 countries have signed up to speak.

In the General Assembly, leaders from several dozen countries will address the 193-member world body including the presidents of Iran and Ukraine, the prime ministers of Japan and the United Kingdom, and the Palestinian leader.

North Korea's race to develop nuclear weapons that could hit the United States dominated Tuesday's opening ministerial session of the assembly.

President Donald Trump threatened to "totally destroy" the Asian nation if the U.S. is forced to defend itself or its allies against aggression. Guterres warned that the threat of a nuclear attack is at its highest level since the end of the Cold War and "fiery talk can lead to fatal misunderstandings."

The treaty bans all countries that eventually ratify it "never under any circumstances to develop, test, produce, manufacture, otherwise acquire, possess or stockpile nuclear weapons or other nuclear explosive devices."

French Foreign Minister Jean-Yves Le Drian told reporters Monday that France refused to take part in negotiations on the treaty because it can only weaken the nuclear nonproliferation treaty, considered the cornerstone of preventing the spread of nuclear weapons. He called the nuclear ban treaty "wishful thinking" that is "close to irresponsible."

But Beatrice Fihn, executive director of the International Campaign to Abolish Nuclear Weapons, said countries signing the treaty will be taking a stand against nuclear weapons, "the only weapons of mass destruction not yet prohibited despite their immense destructive power and threat to humanity." She said that with Trump threatening to use nuclear weapons, the need for the treaty is even greater.

In the Security Council, members are expected to vote on a resolution that would recognize "the primacy of politics" including mediation, monitoring cease-fires and assisting the implementation of peace accords in the U.N.'s approach to resolving conflicts. The draft resolution also underscores the need to enhance the overall effectiveness of peacekeeping operations and "the critical importance of improving accountability, transparency, efficiency and effectiveness."