White House: Undoubtedly Worst Oil Spill in U.S. History

May 25, 2010— -- The oil leak that has spewed millions of gallons of crude into the Gulf of Mexico will undoubtedly become the worst in U.S. history, the White House said today.

"I don't think there is any doubt, unfortunately," Carol Browner, assistant to the president for energy and climate change, told George Stephanopoulos on "Good Morning America" this morning.

BP is expected to try another solution Wednesday, called the "top kill," to stop the leaking well head. BP said there is a 60 to 70 percent chance of success, but Browner declined to put "odds" on the planned attempt.

"We are doing everything in our power to try and make it work," Browner said.

"GMA's" Sam Champion went diving with oceanographer Philippe Cousteau Jr. in the Gulf of Mexico and got a firsthand look at the toxic soup of oil and chemical dispersant that formed large underwater plumes as deep as 25 feet.

Champion reported that the mixture appeared to be breaking into small droplets that are capable of passing through the flesh of fish and birds and being picked up ocean currents.

"[It is] just this cloud of granular oil," Cousteau said. "And you can see it dispersing deeper and deeper into the water column. And, you know, what we're hearing is that there are plumes of oil like this beneath this surface like this at various different depths than can go for 10 or more miles."

Cousteau called it a "nightmare."

CLICK HERE to see Sam Champion's underwater dive in the Gulf of Mexico.

There has been a public dispute about the chemical dispersant and its toxicity.

The Environmental Protection Agency last week ordered BP to use a less toxic chemical dispersant but the company failed to comply. There are fewer dispersants being manufactured in the quantities needed, Browner said, and scientists are continuing to examine how the particular dispersant interacts with the environment.

"What the EPA did yesterday was direct BP to use less of this dispersant while they continue to study what other alternatives may be available," Browner said.

In response to questions being raised about whether BP will follow orders given by the administration, Browner said that BP will "absolutely comply" and is already complying with Monday's order.

"We have the mechanisms to ensure they comply and we will use those mechanisms," Browner said.