The US President Barack Obama has described the huge oil spill in the Gulf of Mexico as an assault on the shores and citizens of the United States.
In a televised address from the Oval Office, Mr Obama accused the oil company BP of recklessness. He said he would tell BP executives to set aside a fund to compensate Gulf coast residents affected by the spill.
It was the US president's first national speech from the Oval Office - a move reserved by presidents for what they see as vital national issues.
He said the spill is testing the limits of human technology.
Oil companies face US Congress committee
The heads of some of the world's largest oil companies have distanced themselves from BP over oil spill.
The bosses of ExxonMobil and Chevron say they would not have used the methods BP did to drill the well, which has been leaking oil since 20 April.
But the head of a key US Congress committee has told them that they are as unprepared as BP.
The chief executives of BP, ExxonMobil, Chevron, ConocoPhillips and Shell - the five largest oil companies operating in the United States - are appearing before the committee, the BBC reports.
Opening the hearing, the joint chairman of the full House energy committee, Henry Waxman, took a tough line, declaring that the major oil firms are "no better prepared to deal with a major oil spill than BP".
ExxonMobil has revealed its emergency response plan includes 40 pages on dealing with the media and only nine on dealing with an oil spill.
Mr Waxman called the five firms' responses "cookie-cutter" plans and "paper exercises", adding: "BP failed miserably when faced with a real leak and one has to wonder whether... [the others] would do any better."
The chief executive of BP America, Lamar McKay, apologised for the impact of the leak but couldn't confirm whether the company would meet government demands and set up a special compensation fund.
The theme of the hearing is deepwater drilling in general; BP chief executive Tony Hayward was to face a separate House hearing devoted to the Deepwater Horizon disaster.
Probe may turn to Marshall Islands
The investigation is expected to turn to the Marshall Islands where the rig was registered. Under international law, offshore rigs such as Deepwater Horizon are treated as ships.
It's been suggested the Marshall Islands is more culpable for the spill than the United States, because the rig carried its flag.
Radio New Zealand International's correspondent, Giff Johnson, says the Marshall Islands operate the third largest ship registry, with more than 2000 vessels flying its flag.
He says investigators have the Marshall Islands in their sights.
Oil containment shutdown forced
BP has temporarily shut down its oil-collection efforts after a collection vessel on the surface caught fire, allowing oil to spew freely into the sea.
The company says it does not know when its oil containment system will restart. Spokesperson Robert Wine says the leak has continued unabated and they are not capturing any oil just now.
BP says it suspects a lightning strike caused the fire at the top of an oil derrick on a drill ship that had been processing captured crude.
There were no injuries.