BP engineers were expected to lower a massive metal containment chamber onto a ruptured oil well in the Gulf of Mexico on Friday in an effort to stem the widening slick. If all goes as planned, the four-story-tall structure will redirect the flow of crude from nearly 1 mile (1.6 km) below the water and pump it up to the surface.

But BP officials warned it will be no easy task.

Oil sloshed ashore on a chain of islands off the Louisiana coast on Thursday as the oil slick expanded. At least 5,000 barrels (210,000 gallons/795,000 liters) have gushed into the Gulf each day since the Deepwater Horizon rig exploded two weeks ago off the Louisiana Coast, killing 11 workers.

BP Chief Operating Officer Doug Suttles had said the dome could be placed over the leak site by late on Thursday and in operation by Monday. The company is drilling a relief well that could take two or three months to complete, making the 98-ton containment dome the centerpiece of the short-term fight against the slick.

On Thursday, the federal government heaped more criticism on BP, and said it would make sure it lived up to its responsibility to limit the damage from what could be the largest oil spill in U.S. history. After meeting with BP executives in Houston, U.S. Interior Secretary Ken Salazar said the company and its partners made "some very major mistakes," although he declined to say whether he meant before or after the explosion.

"Its life is very much on the line here," Salazar told reporters. "Are they doing everything that they can possibly do? I hope that they are. I want to make sure that is in fact happening."

The spill threatens an environmental catastrophe on the coasts of four states and has forced President Barack Obama to rethink plans to open up more waters to offshore drilling. A sheen of oil washed ashore on much of Chandeleur Islands, barrier islands that are part of the Breton National Wildlife Refuge, a U.S. response team spokeswoman said. Some oiled birds, including pelicans and a gannet, had been found, Jeff Dauzat of the Louisiana Department of Environmental Quality said.

The heavier oil remains further off the coast for now, close to the leak site. But the Mississippi Delta, Breton Sound, and Chandeleur Sound are in danger of shoreline contacts over the next few days, officials said. "It has already hit some of the fishing areas further out," said Leonard Ball, a resident of Biloxi, Miss.

"There's already a lot of devastation as far as the fishermen go," he said. In Buras, La., Vietnamese and Cambodian fishermen who are unable make their usual living in the Gulf told BP officials at a townhall meeting that some were excluded from cleanup jobs offered, in part because they are deck-hands rather than boat owners.

"A lot of people are confused. A lot of people are angry. They are not getting the answer they want from BP," said Toan Nguyen, a fisherman who lives on his boat.

By late Saturday or Sunday morning, winds in the Gulf region could pick up to 15 to 20 knots (17 to 23 mph; 27 to 37 kph), a National Weather Service meteorologist said. That may make efforts to battle the slick more difficult.

Calm Weather Window

Crews on Thursday took advantage of calm weather to fight the slick. About 270 boats deployed protective booms and used dispersants to break up the thick oil. Scientists monitored the impact on marine and coastal wildlife of the oil slick, estimated to be at least 130 miles by 70 miles (210 km by 110 km) in size.

Coast Guard and port officials said there had been no impact on ship traffic, and preparations were in place to clean vessels quickly en route to port to keep traffic moving.

In Washington, the Senate Environment and Public Works Committee has slated a hearing on May 11 to examine the spill. Lamar McKay, president of BP America, Steven Newman, head of Transocean, owner of the rig, and Tim Probert, Halliburton's president, have been called to testify. Halliburton helped cement in place the blown-out well.

BP has said it will pay all "legitimate claims," but Alabama Attorney General Troy King called this a "lawyered up" answer and said it should provide "plain-spoken" specifics. A federal statute caps damage recoveries from oil spills at $75 million, if no negligence is established. On Capital Hill, lawmakers are working on a measure to lift it to $10 billion.

The Interior Department on Thursday canceled a series of public meetings planned this month on a proposal to sell oil and gas leases off the Virginia coastline, a move that was cheered by environmentalists.