US President Barack Obama is due to meet relatives of the 11 workers killed in an explosion on the BP oil platform in the Gulf of Mexico.
A presidential spokesman said he would express his condolences to relatives.
BP shares in the UK have fallen to their lowest level since 1997 amid fears of huge US penalties.
US Attorney General Eric Holder said Americans would “not pay a dime” for the clean-up and BP would be held responsible for all damages.
In another development, the Obama administration said BP had agreed to expedite the payment of claims to businesses and individuals whose livelihoods have been disrupted by the spill.
Mr Obama has himself come under mounting political pressure over his handling of the crisis.
Oil has been leaking into the Gulf since the Deepwater Horizon rig exploded on 20 April and sank off the coast of the US state of Louisiana, killing the 11 workers.
President Obama will express his “heartfelt condolences” to their families during the private meeting at the White House, his spokesman Robert Gibbs said.
“And I think he’s eager to discuss with them what their family was telling them about safety conditions and what type of changes can and must be made in the regulatory framework to ensure that deepwater drilling that goes forward is done in a way that is safe and not life-threatening,” Mr Gibbs added.
Amid growing public anger in the US, President Barack Obama is keen to show he is on top of the situation and will make his fourth visit to the region on Monday.
His administration has been steadily applying more pressure on BP, and the US justice department is considering legal action to make sure BP has enough funds to cover the damage and compensate those affected by the slick.
“I can make this pledge to the American people that the American people will not pay a dime for the clean-up of the Gulf region and that BP will be held responsible for all the damages that have occurred,” Mr Holder told reporters in Washington.
“We will take the necessary steps to make sure that that occurs.”
Tracy Wareing, an official at the US National Incident Command office, said an understanding on expediting the payment of claims had been reached at a meeting with BP executives including CEO Tony Hayward.
Administration officials had raised a “pressing concern” about the time BP was taking to provide relief payments, particularly to businesses in the stricken area, she added.
BP says a containment cap system placed on the blown-out well last week collected 15,800 barrels of oil on Wednesday – slightly up on the 15,010 barrels collected in the previous 24-hour period.
The company has come under increasingly sharp attack by some US politicians for its handling of the spill, described as the worst environmental disaster the US has faced.
Shares in the British oil giant have nearly halved over the last couple of months.
The UK government on Thursday sought to play down fears expressed by some senior figures of “anti-British rhetoric” in the US.
Prime Minister David Cameron, who will discuss BP with President Obama this week, said he understood the US government’s “frustration”.
美国司法部长Eric Holder说，美国不会支付任何清理费用，BP将 负全部责任。
自从4月20号Deepwater Horizon钻井平台爆炸并沉没 原油泄露至美国Louisiana海岸的海湾，11名工人丧生
Obama总统在白宫私人会议上对他们的家人表达“衷心的哀悼”， 他的发言人Rober Gibbs说
Mr Gibbs 还说：“他热切的同他们的家人讨论，告诉他们关于安全 状况和如何改进管理体系确保深海钻孔向安全和无生命危险的方向进行”
在美国日益增长的民怨中，Barack Obama 一直保持着掌握大局，并且在周一 将要第4次前往视察该地区。
“我可以向美国人民保证美国人不会为清理海湾地区花费一毛钱，BP将要为产生 的所有破坏负责”Mr Holder 在华盛顿告诉记者。
一位美国国家事故指挥办公室的官员Tracy Wareing说 与BP管理层包括CEO Tony Hayward在内的会议
英国首相David Cameron 本周讲与Obama总统讨论BP，他说能理解美国政府的“忧虑”。