Washington - The US Environmental Protection Agency (EPA) on Friday began a review of the decision under the Bush administration to block California's attempts to introduce its own stringent vehicle-emission provisions.

The move had been widely expected after new President Barack Obama ordered the EPA to take up the matter.

The review marks another reversal of the previous administration's policies and comes just days after Energy Secretary Steven Chu warned that without drastic action on global warming, California's water supply to agriculture and to its cities would become untenable.

Since 2005, California has been trying to get federal approval to introduce regulations placing strict limits on greenhouse-gas emissions from vehicles. The new regulations would likely have forced carmakers to meet the new standards nationwide, because of California's dominant economic position.

After repeatedly delaying a decision, the previous Bush administration rejected the request last year - despite a tradition of the EPA granting California the right to enact its own air- pollution standards.

The review is likely to reverse the denial and encourage other states to adopt similar measures, the agency said Friday.

"The EPA believes that there are significant issues regarding the agency's denial of the waiver," it said in a statement. "The denial was a substantial departure from EPA's longstanding interpretation of the Clean Air Act's waiver provisions. ... Many other states are interested in adopting California's standards." (dpa)