(Adds detail, delegates' concerns, paragraphs 15, 17)

By Irwin Arieff

UNITED NATIONS, Dec 1 (Reuters) - U.S. President George W. Bush's administration is considering a drive to overturn a recent U.N. vote and revive work on a global treaty that would ban medical research on stem cells, diplomats said on Monday.

In a setback for the White House and a victory for the scientific community, the U.N. General Assembly's 191-nation legal committee voted only last month to sideline the treaty for two years.

But the proposal to defer the drafting process until 2005 was approved by a margin of just 80 to 79 with 15 abstentions, and the issue is scheduled to resurface in the full General Assembly next Monday. The assembly's membership is identical to that of its legal committee.

The treaty started out two years ago as a plan to prohibit the cloning of human beings. But the Bush administration -- with the backing of the U.S. anti-abortion movement and many predominantly Catholic countries -- wanted it expanded to outlaw both human cloning and cloning human cells for scientific research purposes.

In anticipation of next week's assembly meeting, the United States and its allies plan to meet at the United Nations on Tuesday to devise a strategy for reversing the committee vote, diplomats said.

U.S. officials said they would have no comment on their plans until later this week.

"We were disappointed by the committee vote and are now looking to see what the next step will be," one U.S. official told Reuters. "A ban on human cloning is of vital importance, and we continue to work a number of angles."

SUPPORTERS' STRENGTH UNKNOWN

A U.N. diplomat, speaking on condition of anonymity, said the group would try to gauge the strength of its support before deciding whether to seek a new vote.

"For some governments, the issue has already been dealt with. But others are eager to plunge back in," the envoy said.

Cloning research relies on embryo cells, or stem cells, because they can grow into all cells and tissues in the body.

Scientists see it as a promising avenue in the battle against many serious diseases while anti-abortion activists and many Catholics see it as the taking of human lives.

There is almost universal support at the United Nations for a treaty banning human cloning, but the international community is deeply divided over therapeutic cloning.

The United States claimed support for its approach from as many as 100 of the 191 U.N. member-nations, but an ad hoc group of governments managed to block it last month by arguing the United Nations should act by consensus on divisive issues.

Word of a possible second round of action on the subject this year has triggered a strong response from the scientific community, which thought the issue had been put to rest.

"I respectfully ask for passage of U.N. initiatives outlawing human reproductive cloning but which allow for the promise of therapeutic cloning," Ian Wilmut, leader of the research team that produced the first cloned mammal, Dolly the sheep, wrote to U.N. delegations this week.

Barring therapeutic cloning would "lose the hope for understanding and treatment of many deadly diseases and conditions," he wrote.

Portuguese U.N. envoy Sebastao Jose Povoas, whose country backs the U.S. position, said some delegations were concerned about the precedent set by the committee vote for a two-year delay when traditionally a one-year delay is called for, but added a vote on reversing it was currently too close to call.