BP is working on a new plan to stop oil that's gushing from a damaged well into the Gulf of Mexico after crews spent three days pumping heavy drilling mud into the site, only to declare the operation a failure.

The company said crews will use robot submarines to cut the pipe spewing the oil and cap it with a funnel-like device. However, BP admits even that option won't stop the flow entirely or capture all the oil.

Workers head to the beach to clean up oil residue in Grand Isle, La., on Sunday. (Jae C. Hong/Associated Press)

BP managing director Bob Dudley, speaking on NBC's Meet the Press, said there's little chance of plugging the well until the drilling of a relief well is completed in August.

He also said it will be at least a week before it's known if the latest manoeuvre will at least reduce the flow of oil.

"As you know, there's 5,000 feet of water. No humans could go down there. We're relying on the robots," Dudley said.

"These guys working offshore are incredibly skilled at this. We've been asking them to do the equivalent of open-heart surgery on television for everyone. They are very, very careful people to check pressures and temperatures and connections, but I would say [BP will know if it works] by the end of the week."

The funnel-like device is similar to a huge containment box that failed before when it became clogged with icelike slush. Dudley said officials learned a lot from that failure and will pump warm water through the pipes to prevent the ice problems.

In a CNN interview Sunday, Dudley said BP officials were uncertain from the start whether the "top kill" method would be a success in plugging the well.

"The top kill operation itself was something that had a level of uncertainty to it because it was just something that was so new and we weren't sure that we were going to be able to pump that mud in and maintain those pressures," he said.

Last week, engineers removed a tube after it sucked up a disappointing 3.4 million litres of oil from the gusher.

The spill is the worst in U.S. history —- exceeding the 1989 Exxon Valdez disaster — and has dumped between 68 million and 150 million litres into the Gulf, according to government estimates.

The leak began two days after the Deepwater Horizon drilling rig exploded on April 20, killing 11 people.

With files from The Associated Press