UNITED NATIONS — Negotiators on Friday narrowly averted the collapse of talks on a world arms trade treaty to regulate the $55 billion global weapons market, agreeing on ground rules for negotiations, with major players the United States and Russia finding agreement on some points but not on others.

Delegates and advocates for tougher oversight of global arms sales said the agreement set the stage for a month-long conference in July to draft the treaty.

There are divisions over whether human rights should be a mandatory criterion for determining whether governments should permit weapons exports to specific countries.

Brian Wood of Amnesty International said Russia, China and several other arms-exporting nations were "resisting proposals from the overwhelming majority for criteria in the treaty that would stop arms transfers" when there was reason to believe that they could be used for serious human rights violations.

He said Washington also had misgivings and was concerned that human rights criteria would discourage states like Syria, a major purchaser of Russian arms, from joining the treaty.

One diplomat described Syria's 11-month crackdown on pro-democracy demonstrations, which has led to the death of more than 5,400 people according to UN figures, and other Arab Spring uprisings as "the elephant in the room" as delegates ponder ways of halting arms sales to governments that kill their own citizens.

"It was in everyone's minds as we discussed the need for the treaty," a senior Western diplomat said.

There was a long debate about whether decisions at the July drafting conference in New York need to be made unanimously, which would give every country a veto.

The United States, Russia, China, Syria, Iran and others pushing for unanimity have argued that the only way to ensure universal compliance is to get all countries on board. Those who dislike the virtual veto, like Mexico and some European countries, believe it could mean that whatever treaty is agreed on in July — if there is one — will be weak.

In the end, participants at last week's discussions at UN headquarters agreed that decisions at the drafting conference in July would be taken by consensus. A senior U.S. official described the veto as "the nuclear option" — a last resort.

The U.S. official, a leading member of Washington's delegation, said the ability to "block a weak treaty" while protecting U.S. domestic rights to bear arms — a politically sensitive issue in the United States — was agreed on in 2009 and remained a condition for U.S. participation.

There are other areas of disagreement, delegates said. Washington does not want the treaty to cover ammunition, while China and Egypt are among those that want to exclude small arms.