Venezuelan state-run oil firm Pdvsa started to move oil revenues to Swiss banks to prevent any likely embargo of funds by Exxon Mobil, amidst a legal battle between Pdvsa and the US's largest oil company, sources told Reuters.

The Texas-based oil major won a court order to freeze Pdvsa's assets -a maneuver intended to secure payment of compensation, after the Venezuelan government last year seized a millionaire heavy-crude oil project Exxon Mobil operated in Orinoco oil belt.

Last Sunday, Chávez vowed to fight back, and threatened to halt oil sales to the US if Washington kept its "economic war" against Venezuela through agents such as Exxon Mobil. US President George W. Bush's administration dismissed the threat as "something we have heard before."

Traders told Reuters that Pdvsa instructed customers to make all payments in Swiss UBS Bank, a few days after Exxon Mobil's lawyers advised banks in the Netherlands Antilles that Pdvsa's accounts should be frozen.

"Everything has to go to UBS in Switzerland now," said a trader under condition of anonymity. A Pdvsa spokesperson declined to make comments.