Venezuela Moves Forward With Oil Nationalizations

"In the event of expropriation, we expect the Venezuelan government to provide U.S. companies with prompt, adequate and effective compensation in accordance with international law," Clay said in Washington.

Oil Minister Rafael Ramirez said some contracts negotiated at last year's soaring crude prices are now overvalued. "We're not going to pay abusive rates to anybody," he said Tuesday.

Venezuela relies on oil for 93 percent of exports, but has seen world oil prices fall 60 percent since their July peak. A barrel of light, sweet crude was trading at $58.73 on the New York Mercantile Exchange on Tuesday.

Under a resolution published in Venezuela's Official Gazette on Monday, 39 companies currently providing services to PDVSA will be brought under government control — including New Orleans-based Tidewater Inc. and Gulmar Offshore Middle East LLC, based in Sharjah, United Arab Emirates.

Some companies not mentioned in the resolution will also be affected by the law, including SIMCO consortium and natural gas processor and distributor Williams Companies Inc. SIMCO's largest partner, Wood Group, is based in Houston. The Wood Group's parent company, John Wood Group PLC, is based in Aberdeen, Scotland.