Global proved oil reserves fell last year, the first drop since 1998, led by declines in Russia, Norway and China, according to BP, the oil firm said in its annual Statistical Review of World Energy on Wednesday.

Oil reserves totaled 1.258 trillion barrels at the end of 2008, compared with 1.261 trillion barrels a year earlier.

"Fossil fuels will remain the dominant source of energy well into the future," BP CEO Tony Hayward said at a presentation in London. The world has enough reserves for 42 years at current production rates, BP said.

BP and other oil companies are struggling to replace reserves as access to deposits becomes harder and older fields in places like Britain and Mexico are depleted. Russia passed a law last year that limits foreign ownership in some of the country's biggest energy and metals deposits. Middle East countries, which hold 60 percent of global reserves, restrict access for international companies.

Some countries have yet to submit information on reserves, making an upward revision of the data likely, chief economist Christof Ruehl said. "Declines in Russia, Norway, China and other countries offset increases in Vietnam, India and Egypt," BP said on its web site.

BP said the estimates in Wednesday's report are a combination of official sources, OPEC data and other third-party estimates.