CARACAS, Venezuela — Chanting "fatherland or death," dozens of President Hugo Chávez's supporters lined up in formation, vowing to defend the country if the United States tries to invade.

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

Chávez is tightening his personal security, accusing the Bush administration 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, Chávez is warning he will cut off oil exports to the United States if it supports any attempt to overthrow him. Venezuela is the fourth-largest supplier of U.S. oil.

The socialist leader called last month for creation of civilian groups to help defend Venezuela if necessary. In response, about 120 supporters in one poor Caracas neighborhood began military-style drills 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 are expected to begin training soon in at least two nearby neighborhoods.

Some of the men and women — street cleaners, retired teachers and the unemployed — wore military patches on their sleeves, even though they are civilians and they have yet to obtain formal recognition from the government. They consider themselves part of the army reserve forces.

Organizer Rafael Cabrices said the group eventually plans to train with weapons to prepare "to defend the fatherland." But Interior Minister Jesse Chacon said that only the military is authorized to carry out armed training and that officials would investigate the group's activities.

Analysts suggest Chávez is lining up alternative allies through oil deals to diminish Venezuela's reliance on the United States, its top oil buyer.

However, Information Minister Andres Izarra said yesterday that Chávez's government "wants to re-establish the best relations with the United States" and hopes there is "a change in policy that is aimed at strengthening, normalizing relations with Venezuela."