Efforts by Secretary of State George P. Shultz and the Greek government to move their relationship into "calmer seas" hit heavy weather instead today because of this week's U.S. military action against Libya.

The leftist government of Prime Minister Andreas Papandreou, which has backed Libyan leader Muammar Qaddafi in the past, walked a delicate line on Libya and on its other grievances against Washington in both its official and unofficial statements, even as anti-American student demonstrators clashed with club-wielding police.

Shultz's effort to get past Papandreou's anti-American rhetoric got off to a shaky start. The international relations committee of Papandreou's PASOK party issued a statement today condemning the U.S. military action in Libya as "the armed enforcement of a new Pax Americana" and an "attempt for a holocaust in the Mediterranean."

This was considerably stronger language than yesterday's official statement by the Papandreou government, which deplored both the U.S. use of force and the Libyan claim to the Gulf of Sidra. Greek political sources said the party statement could not have been issued without Papandreou's approval.

But the fact Papandreou did not say it himself -- as he probably would have if Shultz were elsewhere -- demonstrated that the Greek leader wants better relations with Washington while also feeling a need to satisfy his leftist supporters, the sources said. Asked about the statement, a senior U.S. official said there would be no comment.

Papandreou first spoke of seeking "calmer seas" with the United States during his reelection campaign last year, and the phrase has become the watchword of this leg of Shultz's 10-day European swing.

Shultz used the term on arrival at the Athens airport last night after being escorted on the 75-minute flight from Ankara by first Turkish and then Greek Air Force jets as a precaution against Libyan attack. He used it again today in a luncheon toast to Foreign Minister Karolos Papoulias, with whom he met for an hour and 45 minutes.

At the start of his trip, Shultz told reporters that he wanted to find out "early on, the sooner the better," whether Papandreou intends to make good on another campaign promise: to oust four strategic U.S. military bases from Greek soil when the current Greek-U.S. Defense and Economic Cooperation Agreement expires in 1988.

Shultz also said he would seek stronger Greek cooperation against terrorism and hoped for some sign of movement on resolving the issue of Cyprus, which remains tensely divided between Greeks and Turks.

The outspoken Greek press was uniformly critical of Shultz's expressions of firm support for Turkey during his three-day visit there. One satirical tabloid fronted a portrait of Shultz wearing a red fez, the ancient symbol of Turks, and saying, "The hat may look Turkish, but my mustache proves I am as Greek as Greek can be." Shultz, of course, has no mustache.

Later, about 20,000 demonstrators marched under communist organizations' banners to denounce U.S. "bases of death" at a peaceful evening rally. Several hundred self-styled student anarchists fought with police who denied them permission to march to the rally from the Athens University campus, and another 3,000 demonstrators shouted slogans in front of the U.S. consulate in Salonika.

PASOK student groups and banners were conspicuously absent from the demonstrations, which Greek sources said were brief, small and relatively mild compared to some previous leftist protests here. Shultz was protected by 5,000 extra policemen.

A government spokesman earlier told Greek reporters that Saturday's dynamiting of a statue of President Truman, whose advocacy of military and economic aid helped bring about Greece's recovery after World War II, was "a condemnable act." It was the first official comment on the incident.