CARACAS, Venezuela � As the price of oil roared to ever higher levels in recent years, the leaders of Venezuela, Iran and Russia muscled their way onto the world stage, using checkbook diplomacy and, on occasion, intimidation.

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Dmitry Astakhov/European Pressphoto Agency

Presidents Dmitri A. Medvedev of Russia, left, and Hugo Ch�vez of Venezuela met Sept. 28 in Orenburg, Russia. Their countries plan joint naval exercises.

Now, plummeting oil prices are raising questions about whether the countries can sustain their spending � and their bids to challenge United States hegemony.

For all three nations, oil money was a means to an ideological end.

President Hugo Ch�vez of Venezuela used it to jump-start a socialist-inspired revolution in his country and to back a cadre of like-minded leaders in Latin America who were intent on eroding once-dominant American influence.

Iran extended its influence across the Middle East, promoted itself as the leader of the Islamic world and used its petrodollars to help defy the West�s efforts to block its nuclear program.

Russia, which suffered a humiliating economic collapse in the 1990s after the fall of communism, recaptured some of its former standing in the world. It began rebuilding its military, wrested control of oil and gas pipelines and pushed back against Western encroachment in the former Soviet empire.

But such ambitions are harder to finance when oil is at $74.25 a barrel, its closing price Monday in New York, than when it is at $147, its price as recently as three months ago.

That is not to say that any of the countries is facing immediate economic disaster or will abandon long-held political goals. And the price of oil, still double what was considered high just a few years ago, could always shoot back up.

Still, Russia, Iran and Venezuela have all based their spending on oil prices they thought were conservative but are now close to the market level. Significant further drops could tip the three countries into deficit spending or at least force them to choose among priorities. A worldwide recession, which many economists say is likely, would worsen matters, dampening energy demand and holding down prices.

It is not clear whether the new pressures could create opportunities for the United States to ease tensions, or whether the three countries� leaders will rely more on angry words even if they cannot afford provocative actions. Mr. Ch�vez has continued his overtures to Russia. He, Prime Minister Vladimir V. Putin of Russia and President Mahmoud Ahmadinejad of Iran may now see the United States, hobbled by financial crisis, as even more vulnerable.

Daniel Yergin, chairman of Cambridge Energy Research Associates, a consulting firm in Cambridge, Mass., said oil states were facing something of a reckoning. Originally, he said, they saw the economic crisis as a problem mainly for the United States � but then oil prices went into free fall.

�Now, the producers are experiencing a reverse oil shock,� Mr. Yergin said. �As revenue went up, government spending went up and expectations of a continuing windfall led to greater and greater ambitions. Now they are finding how integrated they are into this globalized world.�

Venezuela

Mr. Ch�vez was emphatic last month when he announced that Venezuela would engage in naval exercises with the Russian Navy in the Caribbean. �Go ahead and squeal, Yanquis,� he said. �Russia�s naval fleet is welcome here.�

The moment, made possible in part by a flood of petrodollars used to buy Russian weaponry, must have been sweet for a man who has spent his presidency wagging his finger at the United States and railing against its capitalist model. Cozying up to Russia, whose leaders have been increasingly at odds with the United States, evoked cold war rivalries in the hemisphere.

Mr. Ch�vez has also used his oil money � in direct payments and through subsidized oil shipments � to win friends in the hemisphere and elsewhere, including President Evo Morales of Bolivia, who expelled the United States ambassador in La Paz last month, saying the envoy was involved in plotting a coup.

Domestic spending in Venezuela has also surged, through the creation of a wide array of social welfare programs that furthered Mr. Ch�vez�s goal of building a socialist-inspired state � and suppressed opposition. The 2009 budget, based on $60-a-barrel oil, includes a 23 percent increase in government spending, to $78.9 billion.

At $140 a barrel for oil, that was conservative. With prices now uncomfortably close to $60 a barrel, economists in Venezuela are expressing alarm over the government�s ability to pay its bills, including those for arms purchases.

Venezuelans are already struggling with an inflation rate of 36 percent, one of the highest in the world.

Mr. Ch�vez said on Saturday that the country could endure any oil price decline, citing its $40 billion in foreign currency reserves, though he then qualified his remarks by saying that oil prices at $80 to $90 a barrel would be sufficient for his plans.