WASHINGTON, May 5 - Senate Democrats are threatening to abandon an agreement to move toward a swift vote on the nomination of John R. Bolton unless the State Department provides documents related to a clash between Mr. Bolton and intelligence officials over assessments of Syria.
The threat reflects growing tensions between Republicans and Democrats on the Senate Foreign Relations Committee over the handling of an inquiry into Mr. Bolton's qualifications to serve as ambassador to the United Nations.
The inquiry is scheduled to conclude on Friday, but the Republican chairman of the committee has refused to endorse a Democratic request for the Syria documents, and the State Department has not turned them over to the panel.
The documents sought by the Democrats include e-mail messages, memorandums, correspondence and draft testimony related to a long-running dispute between Mr. Bolton and American intelligence agencies about Syria. In 2002 and 2003, the Central Intelligence Agency rejected as inflated several attempts by Mr. Bolton to portray Syria and its illicit weapons programs as a threat to the stability of the Middle East.
On Wednesday the committee chairman, Senator Richard G. Lugar, Republican of Indiana, suggested in a letter to Secretary of State Condoleezza Rice that the documents on Syria might be of "marginal relevance" to the inquiry.
But on Thursday the panel's top Democrat, Senator Joseph R. Biden Jr. of Delaware, issued a sharp retort in his own letter to Ms. Rice. "The documents in question go directly to an issue the committee has been pursuing, namely whether in speeches and testimony, Mr. Bolton sought to exaggerate the conclusions that could reasonably be drawn from available intelligence," Mr. Biden wrote.
He warned that he and other Democrats would "consider the failure to produce the requested documents in a timely manner a lack of cooperation" on the part of the State Department, and suggested that such a move would prompt them to seek a further delay in the committee's vote on whether to send Mr. Bolton's nomination to the full Senate, which is now scheduled for May 12.
The nomination could be blocked if the committee's eight Democrats succeeded in persuading at least one of the panel's 10 Republicans to join them in opposing his confirmation. But under committee rules for what constitutes a quorum, Democrats could prevent a vote from taking place if they all refused to attend the May 12 meeting.
A copy of Mr. Biden's letter was made public by his office.
Of nine separate requests for documents submitted last week by Mr. Biden, Mr. Lugar endorsed only five in his letter to Ms. Rice on Wednesday, declining to endorse requests for material related to Sudan and Syria.
But Andy Fisher, a spokesman for Mr. Lugar, said he was not asking the State Department to deny the Democratic request. "If they can and want to provide the information, that's O.K. too," Mr. Fisher said.
A State Department spokesman, Thomas H. Casey, would say only, "We'll respond to all agreed-upon requests."
At the White House, Scott McClellan, the chief spokesman, said the State Department "has been working to make sure that the questions are responded to, and they've been very responsive to the committee."
But Mr. McClellan added, "There's a difference between responding to legitimate concerns and just people trying to go down the road of a fishing expedition."
Another area still being explored by the committee involves Mr. Bolton's use of his authority as an under secretary of state to obtain from the National Security Agency, on 10 occasions, information identifying American officials mentioned in communications intercepted by the agency.
Leaders of the Senate's Foreign Relations and Intelligence Committees have asked the State Department and the security agency for more information about the circumstances of each request, as part of an effort to determine whether Mr. Bolton used his authority properly.
A government official familiar with the discussions said Thursday that the office of John D. Negroponte, the director of national intelligence, was "in discussions" with Senator Pat Roberts, the Kansas Republican who is chairman of the Intelligence Committee, "to determine the best way to meet the committee's needs."
Ms. Rice and the White House have vigorously defended Mr. Bolton's nomination against criticisms focused on his treatment of subordinates and his conduct in disputes over policy and intelligence matters. On Thursday, Mr. Bolton's office made available a letter from another defender, former Prime Minister Margaret Thatcher of Britain, a longtime friend of the nominee.
"A capacity for straight talking rather than peddling half-truths is a strength and not a disadvantage in diplomacy," she wrote. "Particularly in the case of a great power like America, it is essential that people know where you stand and assume that you mean what you say."