The White House is trying to block a tentatively scheduled third appearance before the Senate Foreign Relations Committee by Kenneth L. Adelman, President Reagan's controversial choice to head the Arms Control and Disarmament Agency, according to administration and Capitol Hill sources.

Another committee session for Adelman was reportedly set for 10 a.m. next Thursday during a conversation yesterday between Sen. Charles H. Percy (R-Ill.), the committee chairman, and Sen. Alan Cranston (D-Calif.), who requested the session, according to a Cranston aide.

Cranston, a leader in the effort to defeat the nomination, initially asked for the hearing last Tuesday in order to question Adelman "under oath" about a 1981 news story quoting him as calling arms negotiations a "sham," a Cranston aide said yesterday.

Within hours, however, Percy aides on the committee cautioned reporters that "nothing definite" had been decided about another session. The committee's ranking Democrat, Sen. Claiborne Pell (R.I.), had not been consulted, according to one aide.

But a Percy aide later said another hearing might not be necessary because Adelman had released a "fact sheet" saying he could not recall making the "sham" statement. Adelman also said that the "sham" statement and other sentiments attributed to him in the article were "not consistent with my views."

"We have been firm as we can be that we don't want another hearing," an administration official said yesterday. "Adelman has already been up there for 11 hours and the members have had ample opportunity to question him."

One ranking senator on the committee said the White House is concerned that another hearing "will just stir things up."

Another administration source put it more bluntly: "Cranston is using arms control to run as a Democratic candidate for president and we don't want him using this nomination to help him do it. We don't want any more hearings."

One of Cranston's aims is to call the author of the article, New York Daily News columnist Ken Auletta, and have him put on the record his notes on the conversation with Adelman.

Although Auletta said last night he has not been contacted by the committee, a Reagan aide said such an appearance "will be a real media event."

Getting Percy not to hold another session may involve some of the political "heat" the president promised Wednesday night when he declared his full support for the Adelman nomination.

Percy "has been very accommodating," an administration official said yesterday with some bitterness. "He's waivering on this issue a bit," he said.

Committee traditions, and even its rules, Senate sources said, make it difficult to turn down a request for a hearing if it has the support of the ranking minority committee member, in this case Pell.

The Rhode Island Democrat was unavailable for comment yesterday.

Percy was scheduled to talk last night with Kenneth M. Duberstein, the assistant to the president for legislative affairs. Meanwhile, a White House spokesman said there would be no comment on the matter.

On Capitol Hill, however, Democrats were looking at the possibility that the battle over Adelman could turn into a bitter debate over both arms control policy and the politics surrounding it.

Questions about the competence and views on arms control of the 36-year-old Adelman may become secondary to larger questions about the president's policies.

The administration was embarrassed last Tuesday when it turned out that a majority of the 17-member committee was prepared to vote against Adelman's nomination. Instead, they voted 15 to 2 to sidetrack the vote and give the president an opportunity to withdraw Adelman's name.

Instead Reagan said at a news conference Wednesday night that he would fight for Adelman's nomination.