A woman walks past anti-U.S. graffiti in Caracas, Venezuela, on Friday. (Howard Yanes/Associated Press)The United States has sanctioned two senior Venezuelan officials, accusing them of aiding Colombian rebels in a move that caps a week of escalating diplomatic tension between the two countries.

Hugo Armando Carvajal Barrios and Henry de Jesus Rangel Silva have aided the drug-trafficking efforts of the rebel group Revolutionary Armed Forces of Colombia, the U.S. Treasury Department said Friday.

The move comes as the U.S. was preparing to expel Venezuelan Ambassador Bernardo Alvarez Herrera in retaliation for the expulsion of the U.S. ambassador on Thursday.

Elsewhere, Honduran President Manuel Zelaya said Friday he is indefinitely postponing the accreditation of the U.S. ambassador in a show of support for Venezuela and Bolivia, which has also expelled the U.S. ambassador.

Venezuelan President Hugo Chavez talks to supporters outside Miraflores presidential palace in Caracas on Thursday. (Howard Yanes/ Associated Press)Venezuelan President Hugo Chavez called for U.S. Ambassador Patrick Duffy to leave Caracas Thursday in a televised speech in which he accused the U.S. of plotting a coup to overthrow him. The United States has repeatedly denied the accusations.

In the speech, Chavez recalled his ambassador from Washington, so it isn't clear whether Washington will be able to officially deliver a writ of expulsion to the Venezuelan ambassador if it demands his departure.

Chavez also repeated a threat he has made previously to cut off oil exports to the U.S., its biggest customer.

The earliest that diplomatic relations with the U.S. could be restored, Chavez said, is when longtime foe President George W. Bush leaves Washington in January.

Chavez said he demanded the departure of the U.S. envoy in solidarity with Bolivian President Evo Morales, who expelled the U.S. ambassador to Bolivia on Wednesday.

Anti-government protests

Morales, Bolivia's first indigenous president, has used his first presidential term to nationalize much of the nation's petroleum and mineral wealth. Some of his economic policies have triggered demonstrations in the resource-rich lowland regions of eastern Bolivia, where residents aren't keen to see royalties redistributed more widely among the populace.

Reuters is reporting that Bolivia's government declared martial law in an Amazon region hit by deadly protests on Friday, after violent clashes between Morales's supporters and those of right-wing governors who oppose his reforms.

Two-week-old protests organized by Morales's pro-autonomy opponents in Bolivia's natural gas-rich eastern provinces have been escalating over the past few days.

Eight people were killed Thursday in a clash between the president's backers and opponents. The violence followed the sacking earlier in the week of government offices and seizures of natural gas fields that for two days curtailed gas flows to Brazil by 10 per cent.

Morales ordered the military to restore control of the gas fields. But he has largely lost control of Bolivia's four eastern provinces, whose leaders are fighting with him over gas revenues and a proposed new constitution.

Morales claimed that U.S. Ambassador Philip Goldberg had incited anti-government protests, though he did not offer any specific evidence.

The United States responded by expelling Bolivian ambassador Gustavo Guzman on Thursday.

Relations between Caracas and Washington have been tense for years. U.S. officials have said Chavez poses a threat to democracy, and Chavez has emerged as Latin America's most outspoken — and flamboyant — critic of U.S. foreign policy.

While Chavez has threatened to revoke oil exports to the United States, Thursday's move marks the first time he has expelled a U.S. ambassador.

The developments Friday come amid renewed levels of brinkmanship between the two countries. Russia sent two bombers to Venezuela to carry out military manoeuvres on Wednesday.

Earlier in the week, Venezuela and Russia also announced plans to conduct joint naval war games in the Caribbean in November.

With files from the Associated Press