An international arbitration panel has ruled that Venezuela must pay Exxon Mobil Corp. more than $900 million in a long-simmering dispute over the nationalization of Exxon Mobil's assets in Venezuela's Orinoco Belt, one of the most coveted oil reserves outside the Middle East.

Exxon Mobil waged a legal battle with Venezuela after President Hugo Chavez in 2007 took control of various big projects controlled by foreign oil companies. The move by Chavez came after escalating tensions with Exxon Mobil that included a raid on the company's offices in Caracas, the Venezuelan capital.

The seizing of Exxon Mobil's assets opened the way for the nationalization of dozens of other companies' assets in Venezuela.

Patrick McGinn, a spokesman for Exxon Mobil, said in a statement that the decision by the International Chamber of Commerce confirmed that Petroleos de Venezuela, the country's national oil company, had a "contractual liability" to Exxon Mobil.

Venezuelan officials did not respond to calls Sunday seeking comment on the decision.

Venezuela's energy minister, Rafael Ramirez, said last year that Venezuela had calculated that the country could pay as much as $2.5 billion in compensation to Exxon Mobil and ConocoPhillips, another big U.S. oil company, as a result of the arbitrations over the oil claims.

Despite Venezuela's legal battles over the 2007 nationalizations, the country's oil industry remains open to substantial foreign investment, in contrast to those of other large oil-producing countries like Saudi Arabia and Mexico.

The U.S. oil company Chevron still ranks among Venezuela's largest foreign investors.

The U.S. Geological Survey says the Orinoco Belt, an area with heavy oil in southern Venezuela, has the largest oil accumulation it ever assessed.