Oil giant BP has succeeded in placing a containment cap over the ruptured well head that is gushing oil into the Gulf of Mexico, but was working to seal the cap and close valves before it could capture much of the oil.
"Progress is being made," said Coast Guard Admiral Thad Allen, who is leading the government's response to the oil spill. But it will not be clear for 1-2 days just how much oil and gas can be collected.
The progress comes as winds continued to drive the worst oil spill in US history further eastward, towards Florida's popular and lucrative panhandle beaches.
Clean-up crews were battling the oil over an "extraordinarily wide" area that stretched from Louisiana to Pensacola, Florida, according to Allen. The Coast Guard was investigating reports of an "oily substance" and tar balls by three islands in the Florida Keys.
Late on Thursday, the widening slick struck a pelican rookery in Louisiana, resulting in 60 birds being coated with oil.
"The scope of this thing is starting to extend to the point where it's rather unprecedented," Allen said.
White House officials are already calling it the worst ecological disaster in US history.
President Barack Obama, who has faced some criticism for a slow initial response to the spill, arrived in New Orleans on Friday for his third trip to southern Louisiana since the Deepwater Horizon exploratory rig exploded on April 20.
Obama was to be briefed by Allen and local government officials over the course of the afternoon.
The small containment dome placed over the leak is designed to capture most of the oil and siphon it up to the surface. BP said some had already reached the Discoverer Enterprise drillship about 1.6 km above the leak.
Whether or not the containment cap succeeds in siphoning most of the oil, officials stressed it was a temporary solution. Two relief wells are being drilled that could permanently seal off the underwater leak, but these will not be finished until August.
BP on Thursday managed to cut a portion of pipe that was leaking oil, but the cut was not as fine as hoped, forcing the use of a slightly wider containment cap. Engineers, using robotic submarines operating on the ocean floor, then slowly placed the "top cap" over the marine riser pipe.
"Even if successful, this is only a temporary and partial fix and we must continue our aggressive response operations at the source, on the surface and along the Gulf's precious coastline," Allen said.
The top cap marks BP's latest effort to limit the flow - estimated at anywhere from 12,000 to 25,000 barrels of oil per day - out of the ruptured well head. The beleaguered company has tried in vain for weeks to plug the leak.