CARACAS - President Hugo Chavez has thrown out the US ambassador to Venezuela and threatened to cut off oil supplies, further escalating tensions with Washington just two days after Russia sent two strategic bombers to Caracas in a move unseen since the Cold War.

Photo taken in Caracas in October 2007 of the then new US ambassador in Venezuela Patrick Duddy talking to the press after his accreditation. Venezuelan President Hugo Chavez ordered the US ambassador to leave the country within 72 hours on September 11, in an act of solidarity with Bolivia which also expelled its US envoy, after accusing him of contributing to divisions in the country. (AFP/File/Pedro Rey) The leftist South American leader, ever a vocal opponent of what he has called America's "evil empire", said he was expelling Patrick Duddy "in solidarity" with Bolivia's Evo Morales, who expelled Washington's ambassador to La Paz on Wednesday.

"Starting at this moment the Yankee ambassador in Caracas has 72 hours to leave Venezuela," Mr Chavez said at a public event in the port city of Puerto Cabello, 120km (75 miles) west of Caracas.

He then threatened to cut halt exports of crude oil to the United States if it displayed any aggression towards Venezuela. Despite years of tensions between the two countries Venezuela continues to be one of the United States' main overseas oil suppliers.

"If there is any aggression towards Venezuela" from Washington, "there would be no oil for the people of the United States," Mr Chavez said last night. "Go to hell, Yankees!" he thundered in an invective-laced speech against the US government.

The move caps a week of brinkmanship reminiscent of the Cold War era. On Wednesday, two Tupolev Tu-160 bombers arrived in Venezuela from Russia to carry out military manoeuvres, amid an ongoing standoff over the recent conflict in Georgia.

Just days before, Caracas and Moscow had announced plans for joint war games in the Caribbean involving a nuclear cruiser.

Though both countries denied that the exercises were related to the Georgia conflict, military analysts said Russia's provocative foray into what has traditionally been America's backyard was in response to the presence of US warships in the Black Sea.

The United States has been delivering aid to its ally Georgia as well as taking part in NATO war games in the Black Sea which the Kremlin has denounced as a Western military build-up on its doorstep.

Mr Chavez also announced yesterday that his government had uncovered a coup plot hatched by active and retired military officers, which he said had tacit US approval.

A military prosecutor said two officers - retired general Wilfredo Barroso and retired major Elimides Labarca Soto - will be tried for incitement to rebellion, a charge punishable by five to 10 years in prison.

Mr Chavez, a flamboyant former army colonel who models himself on the Latin American independence hero Simon Bolivar, has long blamed the United States for a failed coup attempt in 2002, as well of a number of other alleged plots. Washington denies all claims of involvement.

The socialist leader has denied that he is looking for a new Cold War, saying of the Russian bombers that their presence was intended to dissuade any aggression towards Venezuela.

"It is a warning," he said."Russia is with us ... we are strategic allies. It is a message to the empire. Venezuela is no longer poor and alone."

However he warned that the deployment signalled the "end of Yankee hegemony" and the beginning of a new "multi-polar world."

The US State Department implicitly linked the development to the crisis in the Caucusus, describing the bombers as "Cold War assets".

"It is something that we will watch very closely, as we have with the movements of other military assets for the stated purpose of this joint exercise," State Department spokesman Sean McCormack said.

"I would just note, for example, that our military assets in the region of the Black Sea, for example, are there to deliver humanitarian assistance," Mr McCormack said.

"I will leave it to the Russians and the Venezuelans to describe the purpose of their activities," he added.

Russia has disputed the humanitarian purpose of the US presence in the Caucusus. Venezuela, which has strongly supported the Kremlin's stance over the conflict, accuses the US of trying to "encircle" Russia through the eastward expansion of NATO to include former Soviet satellites such as Georgia and Ukraine.

The United States is also facing significant challenges elsewhere in Latin America, as leftist leaders rally to Mr Chavez's side to create a socialist bloc to counter American influence.

On Wednesday President Morales of Bolivia ordered the US ambassador to La Paz, Philip Goldberg, to leave, accusing him of contributing to divisions in the country which the government warned was headed towards "civil war." Against a backdrop of increasing unrest, Mr Morales claimed the ambassador had given backing to armed opposition groups challenging his government.

In a tit-for-tat move, the US ordered the expulsion of Bolivia's ambassador to Washington, Gustavo Guzman, after saying that Mr Morales made a "grave error that has seriously damaged" ties.

Challenges to American power in the region were also coming from Argentina, angry over a court case linked to alleged campaign cash from Venezuela for President Cristina Kirchner, and Nicaragua, which has aligned with Russia in recognizing the breakaway Georgian regions of South Ossetia and Abkhazia.