In a tense standoff, BP continued to spray a product called Corexit in the Gulf of Mexico on Monday to break up a vast oil spill, despite a demand by federal regulators that it switch to something less toxic.

The Environmental Protection Agency had set a Sunday night deadline for BP to stop using two dispersants from the Corexit line of products. The oil company has defended its use of Corexit and has taken issue with the methods the agency used to estimate its toxicity.

EPA Administrator Lisa Jackson said the amount of chemicals applied to control the oil spill-- more than 700,000 gallons so far -- was "approaching a world record."

Rear Adm. Mary Landry of the Coast Guard said that while the government had approved the use of dispersant beforehand, "no one anticipated that it would ever be used at this scale and this scope."

It was not clear how the environmental agency would enforce the demand that BP reduce use of dispersants.

"We are continuing to use Corexit while we're still working with EPA on alternatives," Mark Salt, a spokesman for the oil company, said by telephone from Texas.

WHITE HOUSE EXPLAINS DRILL PERMITS

White House officials insisted the administration is denying proposals for new drilling, even though the Interior Department continues approving modifications to existing drilling permits. Carol Browner, the White House's top energy adviser, said the administration's ban amounted to "no new holes" for drilling, even though existing operations have been allowed to continue.

BP'S CEO: 'AS DEVASTATED AS YOU ARE'

Tony Hayward, BP's chief executive, walked along oil-soaked Fourchon Beach in Louisiana and said he had underestimated the possible environmental effects. "I'm as devastated as you are by what I've seen here today," Hayward told reporters after he spoke with cleanup workers in white overalls and yellow boots, some shoveling oily sand into garbage cans. "We are going to do everything in our power to prevent any more oil from coming ashore, and we will clean every last drop up and we will remediate all of the environmental damage."

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