The Obama administration said it wanted to be sure BP would honour commitments not to limit payments for damages to a US statutory cap of US$75m.
Meanwhile, BP says oil dispersants applied at the source of the leak on Friday have begun to take effect.
Mississippi has become the third US State to have oil wash up on its coast.
Crude has already contaminated beaches in Louisiana and Alabama since a drilling rig blew up on 20 April, killing 11 workers.
Mr. Obama has stopped all new drilling for the moment and a number of politicians want that to become permanent.
BP began trying to thread a 6 inch -wide tube into a damaged 21 inch-wide pipe on the ocean floor a mile beneath the surface.
BPâ€™s Chief ExecutiveÂ hoped the leak could be stopped within 10 days.
Â A week ago, BP tried to cap the well with a 100-tonne box, but gave up after it became encrusted with ice crystals.
The spill is threatening to eclipse the 1989 Exxon Valdez leak off Alaska as Americaâ€™s worst environmental disaster.