Demonstrators angered by rationing and shortages are rallying behind opposition leaders who have told Socialist Premier Andrei Lukanov to resign by Thursday or face general unrest.

But Lukanov said leaving office under pressure "would be a betrayal of democracy." There have been two attempted attacks on Lukanov's home recently.On Sunday, about 70,000 protesters outside Alexander Nevsky Cathedral cheered wildly as opposition leaders issued the Thursday deadline for the leader of the long-ruling party and his government to step down.

The Socialist Party was created last spring when the Communist Party dissolved and renamed itself after the November ouster of hard-line leader Todor Zhivkov.

The Socialists won a parliamentary majority in June's free elections with promises to abandon Marxism. But the Lukanov government has proven ineffective and his popularity has slumped with Bulgaria's economic performance.

"The government's one-year credit is up. It is now time for action," Petar Beron, leader of the main opposition Union of Democratic Forces, told the crowd on Sunday.

He promised a showdown in the 400-seat Grand National Assembly on Thursday when a controversial budget reform package is put forth by the Socialists.

"We will wait no longer . . . we will vote against the government's budget draft," Beron shouted from the cathedral steps.

The crowd had jeered and whistled when he called for patience and a parliamentary solution. They yelled "General strike!" and "Death to the Communist Party!"

"If the government doesn't resign on Thursday, the Socialists' fate is in your hands," Beron told the crowd.

Lukanov has pinned his political fate to the budget package, which includes sharp price rises on 21 basic goods at a time when Sofia stores are bare and electricity, gasoline and some foodstuffs are rationed.

Despite his majority in parliament, Lukanov has urged also opposition support for the reforms, citing their national importance. The premier is under increasing pressure from street protests and from some factions within Socialist ranks.