Exxon convinced a court in January to freeze the assets of Venezuela's state oil company so cash would be available if it won arbitration over an oil field which was lost in President Hugo Chavez's nationalisation drive.
But after hearing Petroleos de Venezuela's arguments, the judge ruled against Exxon.
"The injunction granted against the defendant, Petroleos de Venezuela, should be discharged," Justice Paul Walker told the court.
The world's largest non-government controlled oil company by market value, Exxon has the right to appeal but its lawyers declined to comment immediately on whether they would do so.
PDVSA's lawyers also declined immediate comment.
Venezuela's Ambassador to Britain, who arrived shortly after the ruling, answered with just one word when he heard the result: "Excellento".
The judge said he would make the reasons for his ruling available on Thursday.
The initial freeze hit the value of Venezuelan government bonds on international debt markets and enraged Chavez, who threatened to cut off oil supplies to the United States.
Exxon also secured $12 billion freezes in the Netherlands and Dutch Antilles which may now be challenged.
Last Mod: 18 Mart 2008, 17:09