A leading U.S. senator has rejected allegations by Venezuelan President Hugo Chavez that Washington is seeking to destabilize the South American nation. In Caracas, VOA's Brian Wagner reports Mr. Chavez is in a tightly contested constitutional referendum that could allow him to stay president as long as he likes.

Venezuela's President Hugo Chavez waves to supporters at a rally in support of changes to the nation's constitution in Caracas, 30 Nov 2007

President Chavez has leveled a series of allegations against the United States in recent days, such as forming plans to interfere in Sunday's election, topple his government or use CIA agents in Colombia to assassinate him.

Late Saturday, the Venezuelan leader renewed a threat to halt oil sales to the United States if attacked.

Mr. Chavez said if the United States harms Venezuela, Americans will have to look for new oil sources because Venezuela will end its supply.

Venezuela is the fourth largest supplier of foreign oil to the United States, and sends more than 60 percent of its production to U.S. facilities.

In Washington, Democratic Senator Carl Levin denied President Chavez's claims, saying there are no such plans to act against Venezuela's government.

"First of all we are not seeking to destabilize him," said Senator Levin. "His policies, his efforts at dictatorship, to amend the constitution so he can stay there for life, that is what is destabilizing Venezuela, not our policies."

Senator Levin told CNN television that he doubts Venezuela would actually halt oil sales in any event, because he says it relies heavily on U.S. buyers. He added that threats to stop U.S. oil imports, like those from Mr. Chavez, reinforce the need to develop new sources of energy.

Venezuelans voted Sunday in a constitutional referendum that would, among other things expand presidential powers and scrap limits on how long Mr. Chavez can stay on as president.