WASHINGTON – President Bush’s drive to make John Bolton the American ambassador to the United Nations got sidetracked yesterday as Senate Democrats forced a delay until next week of an important confirmation vote.

In buying time, they hoped to win over a pivotal Republican on the Senate Foreign Relations Committee, Senator Chafee of Rhode Island, by amassing evidence that Bolton harassed American officials who challenged his judgment on weapons issues.

Mr. Chafee said yesterday he is leaning toward supporting Mr. Bolton, which would all but assure Mr. Bolton’s confirmation. Mr. Bolton, currently the undersecretary of state, has rejected the accusations.

A committee vote, tentatively planned for today, was scrubbed after Democrats objected, said Andy Fisher, spokesman for the chairman, Senator Lugar, a Republican of Indiana.

Under Senate rules, at least one Democratic senator has to attend a meeting for a vote to occur.

Democrats want further questioning of Mr. Bolton in writing and they are seeking testimony by three American officials on what lawmakers said were Mr. Bolton’s efforts to remove the dissenting analysts. Mr. Fisher said the three officials already had been interviewed by committee aides and their statements were made public.

The postponement was agreed to by Mr. Lugar and the committee’s senior Democrat, Senator Biden of Delaware, said Norm Kurz, an aide to Mr. Biden.

Republicans hold a 10-8 committee majority. Unanimous GOP support would send Mr. Bolton’s nomination to the GOP-controlled Senate, where approval is considered likely.

The committee, in two days of hearings this week, heard from two witnesses, Mr. Bolton and Carl Ford Jr., a former chief at the State Department’s bureau of intelligence and research.

Mr. Ford denounced Mr. Bolton as a bully and a “serial abuser” of lower-level officials who challenged his assessments of the weapons potential of Cuba and other nations.

In a letter to Mr. Lugar, Senator Dodd, a Democrat of Connecticut, requested an additional hearing in which three officials would testify on Mr. Bolton’s dealings with intelligence analysts. Mr. Dodd described Mr. Bolton as “evasive.”

Secretary of State Rice took issue with Mr. Ford’s characterization of Mr. Bolton as a bully. Ms. Rice said she believed strongly in the “role of debate, the role of the open and free exchange of ideas.”

But, she said, when decisions are taken, “I fully expect that people will support those decisions because there is only one president of the United States and that’s President Bush.”

Meanwhile, new allegations postponed a vote on an FDA nominee yesterday. Anonymous allegations against Lester Crawford, President Bush’s choice to head the Food and Drug Administration, prompted the Senate Health Committee to postpone a vote on his nomination yesterday and request an internal FDA investigation.

The panel had scheduled a session to consider Mr. Bush’s promotion of Mr. Crawford from acting to permanent head of FDA. But the committee’s chairman, Senator Enzi, a Republican of Wyoming, and the ranking Democrat, Senator Kennedy, a Democrat of Massachusetts, announced, “We are postponing the scheduled vote on Dr. Crawford’s nomination to provide more time to address issues that have been raised on both sides of the aisle.”