White House officials yesterday sought to tone down press reports from West Germany that President Carter had asked former Chancellor Willy Brandt to act as an intermediary between Washington and Moscow to ease tensions between the two superpowers over the crisis in Afghanistan.

The West German weekly news magazine Der Speigel reports in today's edition that Carter approached Brandt about such a mission during Brandt's visit to Washington earlier this month.

Administration officials, asked about the report, said there was "no specific request" made to Brandt and cautioned against any suggestion that Brandt had some kind of a charter to serve as a mediator.

These officials, however, acknowledged that Carter and Brandt discussed Afghanistan and added that the administration was open to any effort to resolve the crisis in favor of a nonaligned Afghanistan.

The magazine also said that when Brandt returned to Bonn, he met with the Soviet ambassador to West Germany who reportedly asked Brandt to undertake the same kind of mission to reestablish communications between Washington and the Kremlin.

A spokesman for Brandt in Bonn yesterday said the magazine story was speculative, but he would not confirm or deny it. He said there were no firm plans for Brandt to go to Moscow.