An Arab mediator is negotiating with pro-Iranian Shiite extremists in Beirut for the release of West German hostage Rudolf Cordes, the Lebanon News Agency reported Saturday.

The privately owned agency said the unidentified Arab has in the past two days contacted a pro-Iranian group believed to be holding the West German.Cordes, 53, a Middle East manager for the West German Hoechst AG chemical company, was kidnapped in west Beirut on Jan. 17, 1987.

A group calling itself Holy Warriors for Freedom claimed last year that it was holding him along with a West German engineer, Alfred Schmidt. Schmidt was released Sept. 7.

The report quoted diplomatic sources as saying the Arab mediator met with the group at "the consulate of a Western country in Beirut."

"The mediator has left and will return soon carrying answers to a number of conditions laid down by the kidnappers," the agency added, without elaboration. The report did not identify the diplomats.

The report could not be independently verified.

Also Saturday, the Beirut newspaper As-Safir published messages to kidnapped British television journalist John McCarthy from his parents and friends.

In Moscow, a Soviet newspaper published an emotional outpouring of support for American hostage Terry Anderson, 40, who has been held longer than any other foreigner in Lebanon.

The article in Sovietskaya Rossiya urged Anderson to be strong and assured him his captors would be punished. Anderson, chief Middle East correspondent for The Associated Press, was kidnapped March 16, 1985.

"Hold on, Terry!" the paper said. "We want you to know that here in Russia our hearts too are gripped with pain and indignation, when we try to imagine your anguish and sufferings."

McCarthy, 31, a journalist with the London-based Worldwide Television News, was kidnapped April 17, 1986, as he drove to the Beirut airport to board a plane for London.

"Darling John, longing to have you home again. Thinking of you every second. Keep your spirits up. Love, mother and father," one of the messages in As-Safir said.