Washington: The US Senate on Tuesday approved a plan that would enable the federal government to sue the Organisation of Petroleum Exporting Countries (Opec) for price manipulation, but the White House has threatened to veto the measure and opponents warned Opec members could retaliate by turning off the taps.

The bill would revoke the sovereign immunity Opec members enjoy from US legal action. It would allow the Justice Department to sue Opec nations in US courts.

The Senate voted 70-23 to attach the proposal to energy legislation that the chamber is expected to vote on by the end of the week. The body had approved a similar measure in 2005 but it was dropped before the bill was finalised.

Fear of backlash

The White House has threatened to veto the measure, and even if it became law, the Bush administration's Justice Department would have to initiate any lawsuit.

The bill's opponents admitted that it was popular but warned that Opec nations - source of about a third of the world's oil - could reciprocate and sue the US in their courts.

With Americans frustrated at gasoline pump prices above $3 a gallon, Congress members have called for the US to insulate itself from foreign oil producers.

A labour group sued Opec in 1978, but a US appeals court rejected the case on the grounds that Opec's members were immune to lawsuits because their decisions were "acts of state" on behalf of foreign governments.