CARACAS, Venezuela — Venezuela’s state oil company said yesterday that it has stopped selling crude to Exxon Mobil Corp. in response to the American oil company’s drive to use the courts to seize billions of dollars in Venezuelan assets.

Exxon Mobil is locked in a dispute over the nationalization of its oil ventures in Venezuela that has led President Chavez to threaten to cut off all Venezuelan oil supplies to America. Venezuela is America’s fourth largest oil supplier.

Yesterday’s announcement by state-run Petroleos de Venezuela SA, or PDVSA, was limited to Exxon Mobil, which PDVSA accused of “judicial-economic harassment” for its efforts in American and European courts.

PDVSA said it “has paralyzed sales of crude to Exxon Mobil” and suspended commercial relations with the Irving, Texas-based company.

“The legal actions carried out by the U.S. transnational are unnecessary … and hostile,” PDVSA said in the statement. It said it will honor any existing contracts it has with Exxon Mobil for joint investments abroad, but reserved the right to terminate them if permitted by the terms of the contracts. The impact of the decision on Exxon Mobil, the world’s biggest publicly traded oil company, was not immediately clear. Both Mr. Chavez and Oil Minister Rafael Ramirez previously said the company is no longer welcome to do business in Venezuela.

Venezuela’s decision leaves up in the air the situation of a refinery in Chalmette, La. — a joint venture supplied by Venezuelan oil in which PDVSA and Exxon Mobil are equal partners.

Exxon Mobil executives did not immediately return a call seeking comment.

Exxon Mobil is challenging the Chavez government’s nationalization of one of four heavy oil projects in the Orinoco River basin, one of the world’s richest oil deposits.

A British court issued an injunction last month temporarily freezing up to $12 billion of PDVSA’s assets. Exxon Mobil also has secured an “order of attachment” from U.S. District Court in Manhattan on about $300 million in cash held by PDVSA. A hearing to confirm the order is scheduled for today.

Other oil companies including Chevron Corp., France’s Total, Britain’s BP PLC, and Norway’s StatoilHydro ASA have negotiated deals with Venezuela to continue as minority partners in the nationalized projects. ConocoPhillips and Exxon Mobil balked at the government’s tougher terms and have been in compensation talks with PDVSA.

Earlier yesterday at an energy conference in Houston, Exxon Mobil senior vice president Mark Albers declined comment on any court proceedings with Venezuela, though he said the company is eager to negotiate fair compensation for its assets.

Exxon Mobil is taking the dispute to international arbitration, to which Venezuela has agreed. Its legal actions essentially seeks to corral Venezuelan assets ahead of any decision by the arbitration panel.