Washington, May 13 (DPA) US President Barack Obama Wednesday formally threw his weight behind moves in Congress to increase the liability of oil companies for expenses and damages after oil spills.

The proposal would retroactively affect energy company BP for the crude oil well rupture it is now fighting in the Gulf of Mexico, White House officials told reporters.

The ruptured deepwater well is spewing 5,000 barrels of crude a day into the water and threatens a "massive and potentially unprecedented environmental disaster," said Carol Browner, Obama's assistant for energy and climate change.

Officials declined to say whether the White House would support lifting liability for damages to $10 billion, as has been proposed in Congress. Current law requires BP to pay the cleanup costs, but limits its liability for other costs like environmental damage to $75 million.

"We think it's important to work with Congress in determining what the right number is," Browner said.

The bill would also raise the limit on claims against a special oil spill liability fund from $1 billion to $1.5 billion per incident. The $500 million limit on natural resource damage claims would be raised to $750 million.

Testifying before Congress Tuesday, BP America's chairman Lamar McKay pledged to pay out on all legitimate claims, and said his company had already started reimbursing some people along the Gulf of Mexico for temporary loss of livelihood.

Browner drove home the point, reminding reporters of McKay's pledge Tuesday of "liability, blame, fault, put it over here."