The United States yesterday dismissed Soviet President Leonid Brezhnev's opening offer in the negotiations over medium-range missiles in Europe as "nothing that is significantly new," but took comfort that a dialogue on the issue has begun.

The official reaction, released by the State Department last night after a long delay due to the interagency clearance process, was less positive in tone than some comments earlier in the day by White House officials.

Presidential counselor Edwin Meese III called Brezhnev's offer "a step in the right direction . . . a hopeful sign that they, too, will negotiate in good faith." Meese went on to say that "the fact that Brezhnev has made that first step indicates he realizes the president is serious."

State Department officials were not surprised that Brezhnev sweetened his original proposal for a moratorium on further deployment of Soviet missiles in Europe by saying that an unspecified number of weapons would be eliminated unilaterally.

Moving from a standstill to some reductions, while remaining within their preferred framework for other elements of the talks, was considered a likely early move by the Soviets.

The State Department called the Brezhnev plan as presented in Bonn "another version of the old moratorium proposal which the Soviets have made on several occasions beginning in 1979."

The U.S. statement added, "We would hope that President Brezhnev's willingness to consider reductions is a sign that the Soviets are beginning to see the advantages of pursuing genuine arms reductions in this area."