UPDATE 1-US will "push" out BP if spill response falls short

(Recasts, adds quotes, details)

HOUSTON May 23 (Reuters) - The U.S. government will move aside BP (BP.L) from the operation to try to halt the Gulf of Mexico oil spill if it decides the company is not performing as required in its response to the well leak, U.S. Interior Secretary Ken Salazar said on Sunday.

"I am angry and I am frustrated that BP has been unable to stop this oil from leaking and to stop the pollution from spreading," Salazar told reporters after visiting BP's U.S. headquarters in Houston.

"We are 33 days into this effort and deadline after deadline has been missed," Salazar added, referring to the failure of containment efforts attempted so far by London-based BP to control the gushing undersea well one mile (1.6 km) down on the ocean floor.

President Barack Obama's administration is facing growing public and political pressure to take full charge of the oil spill containment operation as criticism against BP grows.

The spill is threatening an ecological and economic disaster along the U.S. Gulf Coast.

"If we find they're not doing what they're supposed to be doing, we'll push them out of the way appropriately," Salazar said, but he did not specify at what point this would occur or what might be the trigger for it.

"This is an existential crisis for one of the world's largest companies," he said, in a reference to the billions of dollars of cleanup and damages costs that BP faces.

Salazar also said BP had agreed to pay cleanup costs beyond the $75 million liability limit set by current U.S. law.

(Reporting by Chris Baltimore; Editing by Pascal Fletcher and Will Dunham)