BP was confident Saturday its latest attempt to capture much of the oil flowing into the Gulf of Mexico will succeed even as the company disclosed yet another setback in their experiments to curb one of America's worst environmental disasters.

BP believes it can hook up its mile-(1.6-kilometer)long tube to suck oil from a blown-out well, despite an earlier snag with connecting two pieces of equipment. If successful, it would be the first time the company has captured any of the oil since a rig sank April 22 and millions of gallons (liters) of crude started spewing into the gulf.

The company also began spraying dispersants beneath the sea Saturday and said the chemicals appears to have reduced the amount of surface oil. The spraying is a contentious development because it has never been done underwater.

Technicians have been working since early Friday to insert the tube into an oil pipe a mile (1.6 kilometer) beneath the surface using robotic submarines. The tube is intended to suck oil up like a straw to a tanker on the surface, while a stopper surrounding it would keep crude from leaking into the sea.

Engineers trying to connect the lengthy tube to framework on the bottom of the ocean ran into trouble Friday, BP chief operating officer Doug Suttles said. The framework had to be brought to the surface to be adjusted.

The framework was returned to the ocean floor, and engineers were attempting again to hook it up. They hoped to start bringing up oil by Saturday night, Suttles said.

If it works, BP thinks it would contain more than three-quarters of the leak. A smaller leak is several thousand feet (meters) away at the site of the blowout preventer.

The insertion tube and dispersants are the latest of several efforts to fight the massive spill. The company has also tried to contain the leak with a 100-ton box and burn small amounts of oil at the surface.

Federal regulators on Friday approved the underwater use of the chemical dispersants, which act like a detergent to break the oil into small globules and allows it to disperse more quickly into the water or air before it comes ashore.

The decision by Environmental Protection Agency to allow the chemicals to be used below the surface angered state officials and fishermen, who complained that regulators ignored their concerns about negative effects on the environment and fish.

"The EPA is conducting a giant experiment with our most productive fisheries by approving the use of these powerful chemicals on a massive, unprecedented scale," John Williams, executive director of the Southern Shrimp Alliance, said in a news release.

The shrimpers' concerns come a day after Louisiana Health and Hospitals Secretary Alan Levine sent a letter to BP outlining similar concerns. BP and the Coast Guard said several tests were done before approval was given.

"We didn't cross this threshold lightly," Coast Guard Rear Adm. Mary Landry said. "This is a tool that will be analyzed and monitored."

Meanwhile, Secretary of Homeland Security Janet Napolitano asked BP to make clear in public if they will limit how much they pay for cleaning up the spill and compensating people hurt by it.

In a letter to BP's CEO Tony Hayward, she noted that he and other executives have said they are taking full responsibility for cleaning up the spill and will pay what they call "legitimate" claims. Napolitano said the government understands this to mean that BP will not limit its payments to a $75 million cap set by law for liability in some cases, and called on BP to say clearly if it will ignore the cap.

"The public has a right to a clear understanding of BP's commitment to redress all of the damage that has occurred or that will occur in the future as a result of the oil spill," Napolitano wrote.

President Barack Obama assailed oil drillers and his own administration Friday as he ordered extra scrutiny of drilling permits. He condemned the shifting of blame by oil executives and denounced a "cozy relationship" between the companies and the federal government.

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Associated Press writers Janet McConnaughey near Fort Jackson; Jason Dearen in New Orleans; Erica Werner, Matthew Daly and Frederic J. Frommer in Washington, and Melinda Deslatte in Baton Rouge, Louisiana, contributed to this report.