US president Barack Obama promised yesterday to stand with the people of the Gulf Coast "until they are made whole" after the oil spill catastrophe.

And he maintained his forceful tone towards UK oil giant BP, vowing the firm would "pay every single dime owed to the people along the Gulf Coast".

Obama recorded his weekly radio and internet address from Grand Isle, Louisiana, where he made his third trip to the Gulf since a drilling rig explosion unleashed a gusher of crude oil into the sea on 20 April.

He spoke of the people he had met – an oyster fisherman named Floyd whose oyster beds have been destroyed by oil, and Terry, a shrimper who is losing income because shrimp fishing has been shut down.

"These folks work hard," Obama said. "They meet their responsibilities. But now because of a man-made catastrophe – one that's not their fault and that's beyond their control – their lives have been thrown into turmoil.

"It's brutally unfair. It's wrong. And what I told these men and women – and what I have said since the beginning of this disaster – is that I'm going to stand with the people of the Gulf Coast until they are made whole."

Obama reiterated some of the steps his administration has taken to respond to the spill, including mobilising National Guard troops.

He spoke as BP worked on its latest attempt to tame the runaway well 5,000ft beneath the sea, by capping it and trying to siphon off some of the crude.

But oil continues to escape. The damaged rig has disgorged at least 22 million gallons of crude into the Gulf.

"We are prepared for the worst," Obama said, noting that regardless of the outcome, there will continue to be some spillage until relief wells can be completed to permanently control the leak.

That will not happen until August at the earliest.