MOSCOW, JULY 6 -- Populist leader Boris Yeltsin today urged the Soviet Communist Party to form a coalition with newly emerging democratic political forces as the only way of avoiding a "historical defeat" at the hands of the Soviet people.

In a fiery speech to the Communist Party congress, the newly elected president of the giant Russian republic said the party that has ruled the Soviet Union for 73 years risked the same fate as the Communist parties of Eastern Europe unless it adopted major reforms. He even warned party officials that they could be brought to trial for leading the country to ruin.

"Events are developing very rapidly. Any attempt to delay them, which some people are dreaming about, will inevitably lead the party to full historical defeat," said Yeltsin, 59, who was dismissed from the Kremlin leadership in 1987 after criticizing the slow pace of reform.

The 4,700 predominantly conservative delegates listened to Yeltsin's speech in grim silence, with only a smattering of applause at the end. The former Moscow Communist Party chief has practically no chance of convincing the congress to accept his views and appeared to be speaking primarily for the historical record.

Yeltsin's proposals for transforming the Communist Party into a Western-type social democratic party include the dismantling of party cells in the army, KGB and other state institutions, and the voluntary surrender of much of its property. He also suggested the party rename itself the "Party of Democratic Socialism," the name adopted by the East German Communist Party after the overthrow last year of the Stalinist leadership.

Over the past four days, the congress has been dominated by conservative speakers who have fiercely rejected calls for fundamental changes in the party's role in society. Many delegates also have expressed hostility to the idea of a market economy, which President Mikhail Gorbachev has described as the only way of rescuing the Soviet Union from its deepening economic crisis.

Coal miners from the Soviet Union's three largest mining regions today rejected an appeal by the congress to call off a one-day political strike on July 11 to press for the resignation of the government headed by Prime Minister Nikolai Ryzhkov. The miners back many of the demands voiced today by Yeltsin, including the closure of party offices in mines and factories.

July 11 marks the first anniversary of the start of industrial unrest last year in Soviet coal mines that ended only after the government agreed to most of the miners' demands. The strike committees, which formed the backbone of the country's first free trade union movement, maintain that the authorities have failed to keep many of their promises.

Yeltsin told the congress that conservative forces in the party were dreaming of "revenge" for the reverses they have suffered during the five years of perestroika, as Gorbachev's reform program is known. But he said that it was an "illusion" to think that the party apparatchiks would be able to retain any authority in the country even if they emerged triumphant from the congress.

The silver-haired politician called on the congress to take steps to rejuvenate the party and form a "union of democratic forces" with other political groups. Otherwise, he warned, the party would split into radical and conservative wings and "lose its position as a real political force in the country."

As president of Russia, by far the largest of the Soviet Union's 15 republics, Yeltsin already has started to put some of his ideas into practice. A draft decree on power now being considered by the Russian legislature includes a proposal to outlaw political party membership for government officials. Yeltsin has said that he will suspend or review his party membership at the congress.

The congress gave a rapturous reception to a conservative economist, Alexei Sergeev, who has campaigned against the introduction of a market economy.