The Senate Foreign Relations Committee, clearly questioning President Reagan's commitment to arms control, sidetracked the nomination of Kenneth Adelman as director of the Arms Control and Disarmament Agency yesterday to give the White House time to reconsider or withdraw it.

But at his news conference last night, Reagan defended his arms control policies and vowed to back his nominee, even if the committee votes Adelman down and paves the way for a showdown on the Senate floor.

Senate and administration sources said last night that they believed Reagan was prepared to accept a narrow no-confidence vote on Adelman in committee as long as he can win confirmation by the full Senate.

Asked whether he should withdraw Adelman's nomination so as not to harm U.S. arms control negotiating efforts under way in Geneva, Reagan replied: "I think it would be far more destructive to our allies and their peace of mind to see me repudiated by a Senate committee on someone that I want . . . . "

Committee Chairman Charles H. Percy (R-Ill.), faced earlier yesterday with the prospect of an embarrassing rejection of the president's choice by nine of the 17 senators, solicited a motion from Democratic members that would put off the vote for a week or more.

Adelman's critics on the committee contend that he lacks experience and a commitment to arms reduction.

Sens. Charles McC. Mathias Jr. (R-Md.) and Larry Pressler (R-S.D.) indicated shortly before the committee hearing that they would join six of the eight committee Democrats in voting against Adelman.

A seventh Democrat, Joseph R. Biden Jr. of Delaware, who also was undecided before the hearing, said afterward that he had notified Vice President Bush yesterday morning of his decision to vote against Adelman. Biden joined the call for a delay, suggesting that world perception of U.S. arms controls policies would be further harmed if the committee reported Adelman's nomination to the full Senate with an unfavorable recommendation.

Meanwhile yesterday, the Senate voted 81 to 11 to end a year-long conservative challenge to the nomination of Richard R. Burt as assistant secretary of state for European affairs.

The vote came after an unusual closed session of the Senate in which members heard what was reported as a "damage assessment" of a June, 1979, article by Burt that disclosed the existence and capability of a U.S. spy satellite that could monitor Soviet missile tests.

Following the Burt vote, the Senate also confirmed by unanimous voice vote the nomination of Richard T. McCormack as assistant secretary of state for economic affairs. McCormack's nomination had been held up by liberal senators in retaliation for the conservatives' hold on Burt.

The momentum against Adelman was fueled by Sen. Alan Cranston (D-Calif.), who started the committee meeting by presenting two newspaper articles containing statements attributed to Adelman in 1981.

The statements suggested that arms control negotiations are a sham and of little value because they endanger a needed defense buildup.

An ACDA spokesman said that Adelman does not remember making these statements and that they do not reflect his position on arms control.

Reagan said last night that Adelman "knows arms control isn't a sham, that we are as on the level as anyone can be in trying to promote this."

The president described Adelman as "eminently qualified" for the ACDA director's job, and suggested that the delay by the Senate panel has not "done anything to help us in our efforts to get an arms reduction agreement."

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) supported the vote to delay, saying he thought it was good to let the "dust settle" and give the White House time to reconsider. But Baker emphasized that committee members should not take his vote as an indication "that I know the president will take down the nomination . . . . I do not."

The turning point in the committee's consideration of Adelman's nomination was a strongly worded statement by Mathias. He said the president's dilemma on arms control is that he has been caught between "the right wing and the right thing," which has resulted in "a series of inappropriate appointments."

Mathias called on the president to withdraw the Adelman nomination. He said "it is an unhappy coincidence" that the president, his secretaries of state and defense and his national security adviser "are all innocent of experience in the complex and bewildering world of arms control."

The addition of Adelman as ACDA director, he said, would put a fifth man in a top arms control policy position "without experience, knowledge or competence in the field of arms control."

Adelman, 36, is now deputy U.S. ambassador to the United Nations and was nominated by Reagan to replace Eugene V. Rostow, 69, who was fired in January.

Pressler said it appeared to him that Percy did not know Mathias had decided to vote against Adelman until the Maryland senator spoke during the hearing. Until then, Percy had been fighting an attempt by Cranston to call Adelman back for a third round of questioning.

Following Mathias' statement, Percy turned to Cranston and said, "I'm going to ask you to renew your motion" to put off the vote, causing the committee room to erupt in laughter. The motion for the delay was eventually formulated by Sen. Paul E. Tsongas (D-Mass.).

Pressler said he told Adelman and Percy on Tuesday of his decision to oppose Adelman. Yesterday morning, before the committee met, Pressler said he received telephone calls from Bush and Reagan seeking to change his mind. Pressler said after the vote, "I think this nomination is effectively dead."

Biden and Mathias also said they had notified Bush of their decisions before the committee meeting.

A Senate Republican staff member said yesterday that Mathias' opposition to Adelman had been growing "for some while. Like a number of members, he was disappointed in the testimony before the committee."

"The other thing is," the staffer continued, "there are people on the committee who see logical alternatives to Adelman, like Bill William G. Hyland and Brent Scowcroft, who have superb credentials as good Republicans and would receive the applause of the people on the committee."

The vote on Burt ends for now a longstanding battle between Senate conservatives and the State Department over key personnel appointments. Burt had drawn fire from Republican Sens. Orrin G. Hatch of Utah, Jesse Helms of North Carolina, Barry Goldwater of Arizona and others for the 1979 spy satellite article and for internal positions he had taken on arms control issues in 1981 while he was director of the State Department's Bureau of Politico-Military Affairs.

The procedural holds on Burt's nomination were removed, however, after Secretary of State George P. Shultz met with a group of the conservatives during the last week in January in the office of Sen. Paul Laxalt (R-Nev.). After the meeting, one Senate source close to the group said, "The saga of Rick Burt is over."