EAST BERLIN, AUG. 21 -- A political compromise on a date for German unification fell apart today when East Germany's second-largest party defied its leader and rejected the agreement.

The leaders of all East German political factions had agreed that the foundering former communist nation would unite with West Germany on Oct. 14, but the left-leaning Social Democrats in parliament voted late today to refuse to abide by the accord.

The Social Democrats said they would push instead for unification to take place on Sept. 15 because of East Germany's collapsing economy. Party parliamentary leader Richard Schroeder had agreed to the Oct. 14 proposal, and he resigned immediately after his colleagues balked at accepting it.

Parliament may consider the Sept. 15 proposal when it meets Wednesday, but Premier Lothar de Maiziere's conservative Christian Democrats hold a strong plurality of seats in the legislative body and are in the best position to set the date for the historic merger. They want unity to coincide with Oct. 14 regional elections in the five traditional states that East Germany will revert to when the two countries merge.

However, demands have been increasing among East Germans for quick unification so that West Germany can move to calm the political and economic chaos that is growing worse almost daily in the East.

De Maiziere's government -- the first democratically chosen leadership ever in East Germany -- has been staggered by dismissals, resignations and charges of incompetence over the past week. On Sunday, the Social Democrats withdrew from de Maiziere's broad governing coalition in a dispute over unification procedure and de Maiziere's dismissal of four cabinet ministers.

De Maiziere is seeking a definitive timetable for the merger of the German states and the dissolution of economically battered East Germany, where joblessness has skyrocketed and state-run enterprises have struggled to compete with Western competition.

Under the abrogated agreement, the two German states would have become a single nation on Oct. 14, with nationwide elections for a common government set for Dec. 2.

Before the Social Democrats voted to reject the accord, de Maiziere had said that lawmakers would convene Oct. 9 to formalize the Oct. 14 unification date. Oct. 9 is the first anniversary of a massive demonstration in the East German city of Leipzig that sparked other democratic rallies around the country and marked the beginning of the end for the long-ruling Communist government.

Alluding to the attempt by legislators to capture the spirit of grass-roots solidarity that toppled the old regime, de Maiziere said parliament will convene under the motto: "Where we come from, where we want to go."

Agreeing initially on the October date were the Christian Democrats; the Social Democrats; the former Communists, the third-largest party in parliament, and the small Buendnis 90 coalition, which includes intellectuals and human-rights activists who led last year's political uprising.

Christian Democrats in both German states wanted to keep the date of unification and all-German elections as close together as possible, saying this will guarantee representation for East Germans in a unified parliament. The Social Democrats charge, however, that the Christian Democrats were hoping to win the election before West Germans realized the true cost of bailing out East Germany.