Chancellor Helmut Kohl today met with a senior Soviet official for the first time since he took office, and he declared that West Germany would remain a "solid, honest and reliable partner" for the Soviet Union.

However, he qualified his wish for continued East-West cooperation by saying he wants a "genuine detente."

The new West German leader also balanced his reassurances to Mikhail S. Solomentsev, an alternate member of the Soviet Politburo, with "expressions of concern" about "strains" put on East-West relations by the invasion of Afghanistan and "current developments" in Poland.

A one-page West German government statement released after an hour-long meeting in Kohl's office differed little from East-West policy papers issued by Kohl's predecessor, Helmut Schmidt, whose center-left government was ousted last Friday.

The phrase "genuine detente," intended to signal to the Soviets that detente should not be a one-way street, was the official wording adopted by Western alliance leaders after some haggling at a summit meeting in Bonn last June.

In these early days of his center-right coalition, Kohl appears to be staying close to Schmidt's former line, stressing continuity in order to keep the confidence of the national majority in West Germany that favors sustained cooperation with the Soviet Bloc.

A new pro-Western accent is expected to emerge in Kohl's policy, but to what extent remains an open question -- even to senior foreign-policy officials here.

In public remarks so far, Kohl has stated a desire to extend good relations with Moscow while smoothing out differences with Washington.

"What this will mean in practical terms -- say if something happens in Poland over the weekend -- I couldn't say," conceded one Bonn official. "We're not on a very clear footing here yet." There have been reports from Warsaw that the government intends to dissolve the Solidarity union this weekend.

Meanwhile, U.S. Ambassador Arthur Burns conferred with Kohl yesterday, and the chancellery announced that the West German leader hoped to see President Reagan in Washington in mid-November.

The meeting today was described by a German official as "very friendly." Solomentsev told Reuters afterward that he saw "good grounds for optimism" about relations with the new Bonn government.

The German statement said Kohl in the meeting "underlined the calculability of German foreign policy and declared that the Federal Republic would continue to be a solid, honest and reliable partner in relations to the Soviet Union and Eastern Europe on the basis of existing contracts and agreements." It said that "the policies of the Federal Republic are directed towards the active securing of peace, genuine detente, dialogue and cooperation."

Kohl was also said to have appealed to the Soviets to allow the emigration of Germans still living in the Soviet Union who want to leave.

On nuclear arms, Kohl made clear to Solomentsev that Bonn would go ahead with Western alliance plans to deploy new U.S. nuclear missiles in Western Europe at the end of 1983 unless Moscow takes "substantial steps" to reach agreement with the United States in talks to reduce such weapons.