British Petroleum officials are saying it could be Sunday before it's known if efforts to pump heavy drilling mud and debris into the well have succeeded.
As the nation waits, Americans have tuned in by the droves to the live underwater Internet video of the gushing oil to see for themselves if the procedure is working.
Chief operating officer Doug Suttles said the top kill is going as planned. Although the procedure has been stopped several times, scientists say it appears BP is gaining ground.
President Barack Obama spent Friday afternoon in Louisiana for an up-close look at the devastating Gulf Coast oil spill.
The trip was his second visit to the area since the spill and came amid criticism that the administration was not reacting quick enough to the crisis.
Obama has since ordered more manpower to deal with the cleanup.
"Either the boom soaks stuff up, or manually you can pick up these tar balls as they're coming to shore. But obviously the concern is that until we actually stop the flow, we've got problems," Obama said during his viist to the Louisiana coast.
In addition to being briefed on what's being done to stop the leak and clean up the oil, Obama got an earful from frustrated residents.
"The president's been here once in how many days it's been now?" resident Bobby Petre said. "It's over a month it's been spewing."
Overnight, a 30,000-horsepower engine shot drill mud down two narrow tubes in an effort to stop the leaking oil for good. If the drill mud can plug the leaking well, engineers will then plug it with cement.
"I think the real challenge today is going to be to sustain the mud on top of the hydrocarbons and reduce the pressure to the point where they could plug it," U.S. Coast Guard Adm. Thad Allen said. "I think it will be critical in the next 12 to 18 hours."
BP officials say they won't know until Sunday if the top kill procedure is working. CEO Tony Hayward is hopeful for its success.
"I think it's probably at least 48 hours away before we could have confidence that we succeeded," he said. "We've said all along, we rated this at 60 percent to 70 percent. That has not changed."
Government scientists now estimate the well is spewing between 12,000-19,000 barrels a day, making the spill the biggest oil spill in U.S. history.