Soviet-American relations have entered a long period of dormancy as the Kremlin, like Washington, undertakes a deep reassessment of its bilateral positions and cautiously awaits a move from the other superpower.

With a lame duck administration in the United States and President-elect Ronald Reagan only beginning to sift through policy options, the Soviets are now reviewing their own domestic and foreign policies in preparation for the 26th Communist Party congress next February, when new national economic and political goals will be adopted.

The process suggests Soviet interest in new approaches to such troublesome bilateral problems as strategic arms limitation, East-West trade, Middle East peace and Third World adventurism. But there are compelling reasons to believe that beyond quiet exploration of differences with the Reagan administration, the Kremlin will not volunteer any initiatives of its own in the foreseeable future.

In part, this is a result of the past decade of detente.

If Reagan feels that bilateral detente has run its course, the Soviets might not mind. They have greatly expanded trade with the West. Most of Western Europe has an enormous stake now in these detente-era trade and political relations and the Soviets seem confident that they can maintain them regardless of what happens with the Americans.

These factors all bolster Soviet President Leonid Brezhnev's original detente policy. The present dispute between Washington and its NATO allies over defense spending strengthens Moscow's conviction that Europe has at last identified basic interests that are in conflict with Washington's in relation to the Soviet Union.

The importance of the European connection cannot be underestimated in assessing Moscow's position on Afghanistan, the principal bilateral problem between the superpowers. Largely because of trade ties developed through detente, the Kremlin has had considerable success in blunting the impact of the grain embargo and the high-technology trade sanctions imposed by President Carter in retaliation for the Soviet invasion of Afghanistan.

If Reagan relaxes or removes the sanctions, the Kremlin will trumpet it as acceptance of the status quo in Afghanistan -- an effortless victory that will only reaffirm Soviet leaders' judgment that they could intervene without lasting adverse consequences.

The Soviets are now treating Reagan in a friendly manner, part of general leadership policy to await any new leader's actual accession to power. For example, Brezhnev in a Kremlin speech last night for Mozambique's leader Samora Machel, asserted, in what obviously was intended for Reagan's ears:

"I will not touch upon what was said by [Reagan], his supporters and his opponents in the heat of the election struggle. I can only say with a full sense of responsibility that any constructive steps of the U.S. administration in the field of Soviet-American relations and vital international problems will meet with a positive reaction on our part."

Set against official silence here about Reagan's postelection promise to confront Moscow with its "policies of aggression," Brezhnev's statement underscores Soviet hopes that Reagan will turn out to be a centrist like Nixon, capable of finding accommodation behind a facade of tough, anticommunist politicking.

With plenty of economic troubles of their own in addition to the complex political-economic troubles of Poland, the Kremlin is not eager to anger the president-elect in a way that could be seen as challenging him to undertake the all-out arms race he said he favored during the campaign.