Secretary of State Edmund Muskie today dismissed the latest plan for withdrawal from Afghanistan is "cosmetic and not a meaningful proposal" and prepared to discuss the matter in person Friday with Soviet Foreign Minister Andrei Gromyko.

In two brief press conferences amid a day of pomp and celebration geared to the 25th anniversary of the signing of the Austrian State Treaty, Muskie took pains not to raise expectations about his scheduled meeting with his Soviet counterpart.

Muskie said the talks will begin as "a diplomatic minuet as we each recite our reactions to the other's actions over the past six to eight months." He added that there will be "probing" on each side of future possibilities, but "I do not expect a sustantive achievement tomorrow."

At another point, Muskie said of the session with Gromyko, "We must begin and that is what the talks tomorrow are -- a beginning."

There has been no meeting of U.S. and Soviet foreign ministers since last September, before the Soviet invasion of Afghanistan and the indefinite postponement of Senate debate on the strategic arms limitation treaties.

The last comprehensive Soviet-American discussion at top levels was the summit conference of President Carter and Soviet President Leonid Brezhnev here in Vienna in mid-June of last year. At that meeting the SALT II pact was signed, amid expectations of a general improvement in superpower relations.

Muskie and Gromyko will come into their discussion fresh from meetings of the Western and Eastern alliances -- the NATO meeting that ended Wednesday in Brussels and the Warsaw Pack meeting that has been taking place in Poland. NATO reaffirmed its strong opposition to the Soviet invasion of Afghanistan and its determination to strengthen the military position of the West.

The Warsaw Pack, which is also undergoing a military buildup, called for a world summit conference to resolve the present crisis -- less of a full-scale peace offensive than Washington had expected.

The latest proposal on Afghanistan was announced late Wednesday in a broadcast by the Soviet-installed Afghan government of Babrak Karmal and was quickly repeated by Tass, the Soviet news agency. The announcement said the question of "limited military contingents" can be discussed when "agression and other forms of intervention" in Afghanistan have stopped.

Muskie said the Afghan statements seemed timed to influence a coming conference of Islamic states in Pakistan rather than to make "a solid and clear offer" on the withdrawl of Soviet troops.

[Meanwhile, Pakistan rejected peace talks with the Babrak government until Soviet troops withdraw from Afghanistan, United Press International reported. A Foreign Ministry spokesman made the statement as a rejection of the Kabul government's call Wednesday for talks with Iran and Pakistan on a timetable for a Soviet pullout.]

Gromyko may also take up the offer in meetings planned here with British, French and West German foreign ministers, who also are attending the ceremonies to commemorate the Austrian treaty. Gromyko is expected to arrive here from Warsaw at midday Friday.

Muskie, who arrived this morning from Brussels, met with Austrian Chancellor Bruno Kreisky and U.N. Secretary General Kurt Waldheim before attending a commemorative ceremony and the opera.

Friday the new secretary of state is to meet the foreign ministers of France, Italy and Yugoslavia as well as the Soviet foreign minister. After the meeting with Gromyko he is to fly home to Maine for the weekend.