The Latest: 50 nations ink nuke ban pact; big powers oppose

The Latest on a treaty to ban nuclear weapons (all times local):

7:30 p.m.

Fifty countries so far have signed on to the first treaty to ban nuclear weapons. If they follow through by ratifying it, the treaty will take effect.

States began signing the pact Wednesday. The world's existing nuclear powers oppose it, saying a ban could be dangerous.

Guyana, the Vatican and Thailand have already ratified the treaty. The threshold for it to take effect is 50 countries, who by ratifying it, would bar themselves from developing, testing, producing, manufacturing, or otherwise acquiring, possessing or stockpiling nuclear weapons "under any circumstances."

Supporters of the pact say it's time to push harder toward eliminating atomic weapons than nations have done through the Nuclear Non-Proliferation Treaty.

Nuclear powers say the nonproliferation treaty is making a difference.

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4:30 p.m.

More than 40 countries so far have signed on to the first treaty to ban nuclear weapons. But the nuclear powers want no part of it.

Forty-two states put their names to the pact within an hour after a signing ceremony opened Wednesday, and more were signing afterward. Guyana, the Vatican and Thailand also have already ratified the treaty.

If 50 countries ratify it, the treaty would take effect for those that did so.

More than 120 countries approved the treaty in July over opposition from nuclear-armed countries and their allies. They boycotted negotiations.

Supporters of the pact say it's time to push harder toward eliminating atomic weapons than nations have done through the nearly 50-year-old Nuclear Non-Proliferation Treaty.

Nuclear powers say a ban won't work.