The Gulf Coast oil spill is now expected to continue gushing until August after BP’s failed attempt to plug the leak in the underwater well. White House climate and energy adviser Carol Browner issued the warning Sunday during an appearance on CBS’s Face the Nation. Browner said the spill is likely the worst environmental disaster in US history.

Carol Browner: “This is probably the biggest environmental disaster we’ve ever faced in this country. It’s certainly the biggest oil spill. And we’re responding with the biggest environmental response. There could be oil coming up 'til August, when the relief wells are dug. I think, David, it's important to know that there’s not just one being dug, there are two, because we insisted, the government insisted, that there be a second one in case something went wrong with the first one.”

Last week, BP tried to stop the leak by pumping heavy drilling mud into the well, a procedure known as “top kill.” But experts now fear the operation may have further damaged the well and its blowout preventer, threatening future efforts.