Petroleos de Venezuela (Pdvsa) began to move its oil revenues to Swiss banks to prevent a possible seizure of funds from Exxon Mobil, in a legal battle that faces the Venezuelan state with the largest company of the United States.   Traders said that Pdvsa has told its customers that all payments should be made in the bank UBS in Switzerland, days after lawyers Exxon inform banks in the Netherlands Antilles that the accounts of the state holding company must maintain their current balances.

 "Everything has to go to UBS in Switzerland now," said a trader who asked not to be named.  A spokesman for Pdvsa indicated that they had no immediate comment regarding the matter.

 The tactic of Exxon is the biggest challenge so far against a giant oil from Russia to Ecuador governments that have taken advantage of record oil prices to increase their control over concessions to foreign firms.

 The change in bank accounts shows that Pdvsa be reacting slowly to the aggressive legal maneuver that the Venezuelan authorities say knew weeks ago.