The Senate Foreign Relations Committee has scheduled a confirmation vote Thursday morning on Kenneth L. Adelman, President Reagan's controversial choice to be director of the Arms Control and Disarmament Agency.

A committee spokesman said yesterday that the vote will take place after Adelman, 36, the deputy U.S. representative to the United Nations, makes a third appearance before the committee.

The primary purpose will be to answer questions about a 1981 news article that quotes him describing arms negotiations as a political "sham," according to the committee spokesman.

Last Wednesday, nine of the committee's 17 members were prepared to vote against the nomination, but delayed in order to give Reagan an opportunity to withdraw it. However, the president strongly defended Adelman at his news conference that night and threatened to put "heat" on the Senate to get his nominee approved.

Senate Minority Leader Robert C. Byrd (D-W.Va.) announced yesterday that he would oppose Adelman because of his inexperience and "cavalier" attitude during his two previous appearances before Foreign Relations.

Byrd also said that the president made a mistake in threatening to put pressure on senators to vote for Adelman.

Meanwhile, the committee members opposing Adelman were informally discussing how they would proceed, according to a senior Democrat on the committee.

They could attempt to bottle up the nomination within the committee and force the Senate's Republican majority to try to dislodge it by means of a discharge petition in order to send it to the floor for a vote.

Alternatively, they could send it to the Senate floor with a recommendation that it be defeated.