ON THE GULF OF MEXICO — White House energy adviser Carol Browner said on morning TV talk shows that a new assessment found that about 75 percent of the oil from the worst offshore spill in US history, had either been captured, burned off, evaporated or broken down in the Gulf."It was captured. It was skimmed. It was burned. It was contained. Mother Nature did her part," Browner told NBC television.RELATED:BP CEO to be replacedPhoto gallery: Pipeline repaired after China oil spillAlso Wednesday, BP claimed a key victory in its effort to plug its blown-out oil well in the Gulf of Mexico. Declaring it a milestone, BP PLC said mud that was forced down the well was holding back the flow of crude and it was in a "static condition."In the Gulf, workers stopped pumping in mud after about eight hours of their "static kill" procedure and were monitoring the well to ensure it remained stable, BP said."It's a milestone," BP PLC spokeswoman Sheila Williams said. "It's a step toward the killing of the well."The next step would be deciding whether to cement the well, Williams said.