Mikhail Gorbachev's efforts to reform the Soviet Union - though wholeheartedly supported by the United States - is turning into a tightrope act that could cost him his leadership role.

In an unusually candid assessment, the Bush administration released an analysis recently that said the Soviet leader could become irrelevant as the nation teeters on the brink of collapse from within.This startling assessment comes amid growing unrest in the Soviet Union and varying degrees of effort by the 15 republics comprising the country to wrest power from the central government. Foreign policy and defense are the only areas of government left unchallenged by local leaders seeking more autonomy.

Last week, the Supreme Soviet, the central government's ruling body, granted Gorbachev sweeping new powers to take measures to stabilize the economy and to maintain law and order. But that may not be enough.

The most restless states in the Soviet Union are also the biggest and most important ones. They have long-simmering resentments against being ruled by the Kremlin.

In the Ukraine this past weekend, tens of thousands - estimates ran as high as 200,000 - of Ukrainians rallied in Kiev to denounce Communism and to urge rejection of a new treaty offering a more relaxed relationship between the Kremlin and the republics. More and more cries are being heard for outright independence.

Added to the growing unrest reported elsewhere in the Soviet Union in recent weeks, Gorbachev appears on shaky ground.

"I think there is a crisis of authority that's been accumulating for some time," adds Helmut Sonnenfeldt, a specialist in East-West relations at the Brookings Institute. "The central government and the president (Gorbachev) himself are seriously lacking in authority. He (Gorbachev) has this power that he has been getting from the Supreme Soviet, but it is not clear that anybody pays any attention and implements his orders."

To his credit, Gorbachev has shown remarkable staying power. In repeated showdowns with Communist Party hard-liners, Gorbachev has won virtually every important battle. But that was before this latest round of protest within the Soviet Union.

Adding to his problems is a vital potato crop that is rotting in the fields while the economic and agricultural system is in shambles. If the crop is lost, there could be hunger and even famine in the Soviet Union this winter. Famine and the resulting social upheavel might topple Gorbachev from power.

But it's perhaps way too early to count the wily Gorbachev out. Despite the repeated calls for independence and autonomy, most of the 15 republics are ill-prepared economically to go it alone.

Most are finding just how difficult it is to shift from years of state-controlled economics and political philosophy to the dynamic changes that highlight a market-driven economy and democratic politics.

If Gorbachev can bring some semblance of order to the Soviet Union economy using his newly granted economic powers, he may be able to weather this latest storm and remain an important and relevant cog in the future of the Soviet Union.

If not, Gorbachev could find himself presiding over a country that has disintegrated under him, leaving him a leader with no one to lead.