British Petroleum should make clear that they will pay the entire cost of the Gulf Coast oil spill, Secretaries Ken Salazar and Janet Napolitano said today.

In a letter to the BP CEO Tony Hayward, the Interior and Homeland Security secretaries demanded that BP not rely on a law limiting oil spill liability at $75 million.

"The public has a right to a clear understanding of BP's commitment to redress all of the damage that has occurred or that will occur in the future as a result of the oil spill," Salazar and Napolitano wrote.

Legislation is pending in Congress to raise the liability cap to as high as $17 billion. That legislation was blocked in the Senate by Sen. Lisa Murkowski (R-Alaska).

BP executives have previously said publicly that they would not point to the liability cap as an excuse for limiting clean-up payments.

BP Chairman and President Lamar McKay called the cap "irrelevant" in testimony before a Senate panel.