CARACAS/WASHINGTON (Reuters) - The United States imposed sanctions on aides to Venezuelan President Hugo Chavez on Friday in retaliation for his expulsion of the U.S. ambassador, escalating a crisis that raises the specter of a possible oil supply cutoff.

The diplomatic moves and Chavez's threat to cut off oil shipments to the United States sent the OPEC nation's debt prices tumbling and plunged relations between the superpower and one of its top energy suppliers to their lowest point in years.

Chavez warned on Thursday that if he stops selling oil to the United States, world crude prices would immediately double to above $200 a barrel.

The socialist leader leads a growing bloc of left-wing leaders in Latin America and has diversified Venezuela's oil customers in recent years, particularly increasing supply to China.

He said his decision to expel the U.S. ambassador on Thursday in an expletive-laden tirade against "Yankees," was made to support Bolivia's leftist president who is facing violent protests against his government that he blames on interference by Washington.

Washington struck back on Friday with sanctions against two Chavez aides, including Venezuela's former Interior Minister Ramon Rodriguez, for allegedly aiding Marxist guerrillas in Colombia.

It is also possible Chavez knew sanctions were coming against his officials and wanted to take the offensive. Rodriguez resigned unexpectedly last week, and Chavez often uses a strategy that his best form of defense is attack when he is assailed.

Washington was also preparing on Friday to eject Venezuela's top diplomat in the United States, a U.S. official said, although Chavez tried to preempt that move by telling him to pack his bags and come home a day earlier.

Venezuela has some of the largest oil reserves outside the Middle East and despite Chavez's frequent clashes with the U.S. government, he has maintained oil supplies and never before expelled a U.S. ambassador.

Violent anti-government protests have killed eight people in Bolivia, ruled by Chavez's close ally, President Evo Morales.

Bolivia and the United States expelled their respective ambassadors earlier this week after Morales accused Washington of supporting the opposition.

Venezuelan bond yield spreads over U.S. Treasures -- widely seen as a gauge of investor risk perception -- soared 41 basis points to 765 basis points on Friday.

Chavez said he would not restore normal relations with the United States at least until U.S. President George W. Bush leaves the White House in January.

"When there is a new government in the United States, we will send a new ambassador, a government that respects the people of Latin American," he said.

Lehman Brothers' Gianfranco Bertozzi, who analyses how political risk in Venezuela affects the country's debt prices, told investors the market was over-reacting because there had been no concrete oil-related measures.

"This expulsion is really only until the next administration, the election for which is 53 days away, and in the meantime oil is still flowing - although markets seems agitated by the risk of escalation," he wrote from New York.

Chavez was briefly ousted in a 2002 coup that was initially welcomed by Washington. Even after the coup, Chavez did not go so far as to expel the U.S. ambassador.

But tensions between the United States and Venezuela are escalating quickly. Chavez allowed two Russian long-range bombers to land in Venezuela this week and released evidence of an alleged plot to kill him that he says was supported by Washington.

He also reduced U.S. commercial airline flights to Venezuela and warned he would support "armed movements" to back Bolivia's Morales in the event of a coup against him.

Chavez calls the United States an evil empire and has aligned with Russia. Moscow is sending warships for joint naval exercises with Venezuela's military in the Caribbean in November, reviving tensions not seen in the region since the end of the Cold War.

(Editing by Saul Hudson and Kieran Murray)

U.S. sanctions Chavez aides in growing crisis | U.S. | Reuters