MOSCOW, NOV. 19 -- Boris Yeltsin, president of the Soviet Union's vast Russian republic, said today that Russia would reject Soviet leader Mikhail Gorbachev's proposals to increase his executive authority and warned that such new powers could deepen the crisis of leadership in the country.

Making clear that his political differences and personal rivalry with the Soviet leader remained strong, Yeltsin told the Interfax news agency that despite Gorbachev's plan to bring the leaders of the 15 republics into the executive decision-making process, "one senses mainly an attempt to restore {Moscow's} supreme power" over the republics.

Although the Russian legislature does not have authority to pass judgment on Gorbachev's proposals, Yeltsin's authority as the country's most popular politician and head of its largest republic makes his rejection of the plan a serious setback for the Kremlin leader.

Yeltsin, who is in Kiev signing a historic political and economic treaty between Russia and the Soviet Ukraine, seemed especially displeased that Gorbachev did not consult the leaders of the republics before making his proposals in the Soviet legislalure Saturday.

"It would seem that the proposals of all the leaders of the sovereign republics have, in effect, been thrown overboard. This is very disturbing," Yeltsin said. "Russia, at least, will not accept this. . . . I am convinced that all this will not improve matters, but make them worse."

Yeltsin's remarks come as something of a surprise, since Gorbachev's proposals seemed to be a clear concession to the Russian leader's demand for an inter-republic crisis committee to help lead the country. Some of Yeltsin's fellow radical-reformist leaders, many of them severe critics of Gorbachev, welcomed the new proposals. The official news agency Tass had said Sunday that Gorbachev's move "leaves no room for objective criticism" from Yeltsin.

Ukrainian leader Leonid Kravchuk welcomed Gorbachev's initiative, saying that the new presidential powers are not likely to infringe on the sovereignty of the republics and that the plan could be an effective step if the Federation Council of the republics' leaders took hold as a presidential cabinet.

The treaty between the Ukraine and Russia represents what their two leaders called a new "horizontal" relationship of economic, political and cultural ties between two sovereign states. The treaty, in effect, would eliminate Moscow's unquestioned authority over the Ukraine, a republic of 53 million.

While the leaders of the three Soviet Baltic republics, Georgia and Armenia have made clear they are striving for outright independence, Yeltsin and Gorbachev have said they want to draw up a new treaty defining the relationship of the 15 republics to the central government. Their differences are a matter of degree, with Yeltsin favoring far more authority in the hands of the republics.

The differences between the two men were typified today in a debate in the legislature over a proposal on foreign currency. The draft law, which has Gorbachev's approval, dictates that a vast proportion of all foreign currency reserves be controlled by Moscow. Because the ruble is not an acceptable medium of international exchange, whoever controls foreign currency decides questions of imports and exports.

Yeltsin said the bill was "the president's crudest mistake" and that the Russian legislature would refuse to ratify it.

The Congress of People's Deputies, the country's supreme legislative authority, is to meet next month to consider drafts of a new union treaty, and it is also expected to pass Gorbachev's proposals for a realignment of executive power.