BERLIN--West Germany's president yesterday urged Western nations to help East Germany recover from the exodus of its citizens and the mayors of East and West Berlin shook hands in no mat's land to usher in a new era of relations.

East Germany's Communist Party leader called for an emergency party congress and indicated a new slate of leaders will be installed to replace the Old Guard and institute reforms in his changing nation.

Another hole was cut through the Berlin Wall to the roaring cheers of spectators. East Berliners continued to flood the western half of the city, buying all they could afford with their $55 of government "welcome money."

By yesterday afternoon. Burger King was out of beer and Haagen Daz had sold all its ice cream bars.

Unlike the thousands who had abandoned their Communist home land for the West in recent weeks, most people crossing on the weekend were just visiting, taking advantage of the freedom created by Thursday's opening of East Germany's borders. By last night, the border gridlock had eased, and West Berlin's streets were returning to normal.

Reflecting the new open-border policy, East German Defense Minister Heinz Kessler said yesterday that border guards who once shot at their fleeing countrymen, have been told not to use firearms any more in cases of border violations.

But amid the euphoria, there were reminders of the political changes and uncertainty still sweeping through East Germany, which began carving passages through the 29-mile-long Berlin Wall on Friday.

Communist Party chief Egon Krenz called for an emergency party congress next month, the official ADN news agency said. He indicated a new Central Committee will be elected to carry out various reforms aimed at stopping East Germans from going West.

"We need a Central Committee that can carry the full responsibility and enjoys full trust." Krenz was quoted as telling reporters.

Krenz said the current Central Committee would meet today to approve holding the congress. Also today, East Germany's Parliament is to meet to name a Cabinet to replace the one that resigned last Tuesday. The reform-minded party chief of Dresden. Hans Modrow, was expected to be named premier.

Since Krenz replaced hard-liner Erich Honecker as party chief in October, 10 full members of the ruling 21-member Politburo have lost their positions. There also has been pressure for the 163-member policy-setting Central Committee, chosen under Honecker, to resign.

On West Berlin's fashionable Kurfuerstendamm avenue, about 1,000 leftists marched through the streets shouting slogans against German reunification.

An appeal signed by the official Free German Youth movement and representatives of the democratic opposition voiced fears about "the very existence of our country" in the wake of the massive westward stream of visitors.

More than 3 million East Germans headed West over the weekend, while several hundred thousand people made their way to Berlin from other countries to join a 4-day-old celebration.

"The wall will never be what it used to be. It remains a memorial to inhumanity," West German President Richard von Weizsaecker said in a speech in West Berlin's Kaiser-Wilhelm-Gedaechtnis Church.