The start of training for ''Popular Defense Units'' marks a more confrontational stage in U.S.-Venezuelan relations.

Chavez is tightening his personal security, accusing Washington of backing a plot to assassinate him. While U.S. officials seek to isolate a leader who has become a symbol of anti-American sentiment in Latin America, Chavez is warning he will cut off oil exports to the United States if it supports any attempt to overthrow him.

The socialist leader called last month for creation of civilian groups to help defend Venezuela if necessary; in one poor Caracas neighborhood, about 120 supporters began military-style drills last month even though they have not been issued weapons.

''If an invasion comes, we know what we're going to do,'' said Manuel Mayan, 36, saluting during training in a parking lot Tuesday night, the first attended by international journalists.

Other similar units will begin training soon in at least two nearby neighborhoods, said Sgt. 2nd Class Ricardo Nahmens.

The training is only one sign of growing tensions between Chavez and U.S. officials, who have traded increasingly sharp accusations.

State TV shows U.S. officials criticizing Chavez, while playing the ''Star Wars'' theme music for the ''evil empire.'' Observers say a U.S. invasion is highly unlikely, but Chavez's warnings have struck a chord on the streets of the capital, where graffiti now declares: ''If they kill Chavez, he will return as millions.''

Chavez has said his socialist ''revolution'' for the poor is by nature ''anti-imperialist,'' claiming that has angered the United States. Chavez, who is up for re-election next year, has said U.S. plans to support the Venezuelan opposition are an ''obscene interference.''

The president has been busy signing oil deals with countries from China to India. Analysts suggest he is lining up alternative allies through oil deals to diminish Venezuela's reliance on the United States, its top oil buyer.