EAST BERLIN, AUG. 20 -- As his coalition government collapsed around him today, East German Prime Minister Lothar de Maiziere declared he will be his own foreign minister and swore to hold the disintegrating nation's leadership together until German unification.

De Maiziere dismissed a call for his resignation by the opposition Social Democrats, who charged that he is not competent to end the country's economic crisis.

On Sunday, de Maiziere lost the two-thirds parliamentary majority he needed to win approval of a proposed unification treaty with West Germany, but he retains a simple majority, which is enough to keep office.

The Social Democrats pulled their 88 members out of the 400-member coalition to protest de Maiziere's firing of four cabinet ministers over their handling of the economy and to put distance between their party and the policies of de Maiziere, a Christian Democrat, and his Bonn counterpart, West German Chancellor Helmut Kohl.

De Maiziere's announcement today followed the resignation of Foreign Minister Markus Meckel and other Social Democrats in the four-party governing coalition chosen last March in the first free postwar elections here.

But de Maiziere, who has charged the Social Democratic ministers with failing to help their country through its painful transition from communism to a market-based economy, vowed that "the work of the government will continue." He said East Germany will merge with West Germany on Oct. 14, the date he and Kohl favor.

The Social Democrats said they will propose Wednesday that unification be completed immediately after Sept. 12, when the victorious World War II powers are expected to wrap up talks on the matter. "East Germany is on the verge of collapse, and there is only one solution -- quick accession," said Oskar Lafontaine, a West German Social Democratic leader.

Rudolf Seiters, a top aide to Kohl, said Bonn is ready to accept East Germany into the West even if the action is taken this week. "This is not the best way, but it can be done," he said.

De Maiziere appealed to all East German parties to work together to approve a treaty with Bonn and to find solutions to their country's soaring unemployment rate and the crumbling of its industries.

If East Germany does not agree to a unification treaty with Bonn, West Germany is expected to impose its laws on the East after the East German legislature declares its country to be part of the West.