A somewhat embarrassed Reagan administration yesterday objected to the Senate Foreign Relations Committee's planned release of the now-famous "Rowny memo" containing blunt comments about American strategic arms negotiators.

The matter was considered so sensitive that even the letter describing the State Department's objections to release of the memo was classified "confidential."

The memo itself, when delivered to the committee on Monday, carried no security classification. And three days earlier Deputy Secretary of State Kenneth W. Dam told the committee that, except for the names of individuals, there was no reason to classify it.

The memo was first disclosed publicly earlier this month. Edward L. Rowny, the U.S. strategic arms negotiator, had handed it to Kenneth L. Adelman just days after Adelman was announced as President Reagan's choice to head the Arms Control and Disarmament Agency.

The memo, entitled "talking points for a meeting with Ken Adelman," sharply criticized several of Rowny's colleagues on the negotiating team in Geneva and at ACDA headquarters in Washington. It also stated that Rowny would not consider Adelman his boss, but would report directly to the president.

Opponents of the controversial Adelman nomination have been pressing for release of the Rowny memo, with the names deleted, and are seeking release of two documents prepared by Adelman.

Sen. Larry Pressler (R-S.D.) argued yesterday at a Foreign Relations Committee hearing that the documents raise questions about Adelman's judgment and his credibility in testimony before the committee.

Committee Chairman Charles H. Percy (R-Ill.) asked that a vote on releasing the documents be postponed until the State Department could tell members in closed session the problems that would be created by publication of the Rowny memo. That session could not be scheduled, according to committee sources, so the vote on releasing the documents will take place today.

Percy received a letter, classified confidential, from Assistant Secretary of State Powell Moore yesterday that reportedly said the administration's objection to the release was based "on the harm it would do national security," one source said.

At the committee session, Percy said release of the memo would "do more damage" to the American negotiating team in Geneva. Sen. Rudy Boschwitz (R-Minn.) said, "There are things in the memo that will not help the negotiating process."

Percy last week requested State Department approval for release of the Rowny memo, saying that "it reflects absolutely no discredit" on Adelman since he "did not request" the memo and made "no recommendation" based on it.

Sen. Jesse Helms (R-N.C.) said plans to release the memo were part of "a get-Adelman campaign." He called for a "full-fledged investigation" that would get "Rowny back here from Geneva and get him under oath."

While State Department officials and some committee Republicans looked on uneasily, Sen. Paul E. Tsongas (D-Mass.) broke in to say he would second the motion for an investigation.

The White House has gone out of its way to state its support for Rowny since word of the memo first appeared in public print.