President Barack ObamaBarack Hussein ObamaAnother chance to seek the return of fiscal sanity to the halls of Congress Colombia’s new leader has a tough road ahead, and Obama holdovers aren't helping An alternative to Trump's family separation policy MORE's top environmental adviser on Tuesday would not guarantee that the Gulf of Mexico oil spill would be contained by August.

The government and BP are going forth with a plan to dig "relief wells" to cap the spill, which has been described as the worst in U.S. history, which officials hope can end the leak by August. But White House energy and climate change czar Carol Browner said there are no guarantees.

"There is no guarantees here, as you all said," she said on Fox News. "What I am saying is that there is a plan in place, which the government has reviewed, which we think is the most responsible way of proceeding, which is to dig not one relief well, but to dig two relief wells so that we have redundancies in the system."

Several attempts to stop the spill have failed, including the "top kill" procedure that officials nixed last week. The Obama administration and BP have come under increasing pressure from Congress and the public to stop the spill.

But when asked if the August date was "wishful thinking," Browner expressed confidence the spill will have been stopped by then.

"No, I don't think it is wishful thinking," she said. "We are going to be absolutely on this until the leak is plugged."

President Barack Obama has said he takes responsibility for stopping the spill and has promised that the government is in control of the situation. But critics have said the administration has been slow to act and not forceful enough with BP, the company that leased the rig from which oil is leaking.

She also assured that administration officials, such as Energy Secretary Steven Chu and Interior Secretary Ken Salazar, are directly involved in the decisionmaking process.

"There is no bureaucracy involved in this," she said. "We have people in the room making decisions on a real-time basis."