By Adrian Croft and Kristen Hays
KABUL/HOUSTON (Reuters) - Prime Minister David Cameron offered on Thursday to help deal with BP <:BP.LO:>Plc's Gulf of Mexico oil spill, saying he would take it up with U.S. President Barack Obama, as the beleaguered company's shares rebounded from 14-year lows.
Cameron's comments in Kabul marked the first time he had spoken publicly about the crisis. Cameron, who took office in May and is under pressure domestically to stand up for the British energy company, is due to talk to Obama by telephone this weekend.
Obama has been sharply critical of BP. The two leaders' conversation will have to seek a delicate balance between domestic pressures and long-standing U.S.-British ties.
The U.S. president said after meeting Republican and Democratic congressional leaders at the White House that he wanted to update U.S. pollution laws to ensure that victims of the oil spill were fully compensated.
As BP captured more oil from its ruptured deep-sea well, it pleaded for patience from Americans frustrated about the spill, the worst in U.S. history and now in its 52nd day.
The Obama administration kept up the heat, saying it would make sure BP paid all damages and cleanup costs from the spill, which has soiled 120 miles (190 km) of the U.S. Gulf coast and threatened lucrative fishing and tourist industries.
In another sign the spill is spreading, heavier concentrations of oil began washing up on Florida seashores starting late on Wednesday. Until then, debris from the spill had been limited in the state to relatively small tar balls.
BP STOCK VOLATILE
BP was the second-most active stock on the New York Stock Exchange as shares rebounded by more than 12 percent. It had taken a 16 percent dive to a 14-year-low on Wednesday amid concerns over BP's ability to meet mounting costs.
"The stock is obviously volatile as investors try to wager on the outcome of the Gulf oil spill," said Jud Pyle, chief investment strategist at Options News Network, a division of option market maker PEAK6 Investments in Chicago.
Analysts said the company's improved performance was partly due to speculation that PetroChina, Asia's top oil and gas firm, was considering making a bid for BP.
Shares in Anadarko Petroleum Corp and Transocean Ltd, two companies involved in the ruptured offshore well, also jumped. In London trading, BP stocks sank to their lowest level since 1997 before bouncing off their lows and closing 6.7 percent down.
Illustrating the extent of investor concerns about BP, the cost of insuring its AA-rated debt traded for a time at levels normally associated with "junk" status.
BP said in a statement it did not know why its share price had plunged in U.S. trading on Wednesday.
One of the world's largest corporate giants, BP said it had the financial flexibility to deal with liabilities related to the spill, which to date had cost it around $1.43 billion (972 million pound).
'AN ENVIRONMENTAL CATASTROPHE'
In Britain, business leaders urged the government to defend BP -- the biggest single payer of dividends among UK-listed companies -- against U.S. threats to expand the company's liabilities for the spill. Some U.S. lawmakers have also demanded it suspend payment of its quarterly dividend.
Cameron, speaking on a visit to Afghanistan's capital Kabul, said, "This is an environmental catastrophe. BP needs to do everything it can to deal with the situation, and the UK government stands ready to help.
He added, "I completely understand the U.S. government's frustration. The most important thing is to try to mitigate the effects and get to grips with the problem. It's something I will discuss with the American president when we next talk."
The Obama administration has markedly toughened its rhetoric towards the company in recent days, reflecting U.S. public anger over the oil giant's handling of the spill.
Obama, under fire from some critics who view him as too detached from the crisis, met at the White House on Thursday with relatives of the 11 workers killed in the explosion of the offshore oil rig on April 20 that triggered the disaster.
He assured them that his plan to expand off-shore drilling was on hold "until we have the proper safety measures in place to ensure that a tragedy like this never happens again."
Ratcheting up the pressure on BP, U.S. Attorney General Eric Holder told reporters the "American people will not pay a dime" for the clean-up of the Gulf region and pledged to hold the British company financially responsible.
SPOTLIGHT ON BP DIVIDEND
A senior Democratic politician joined calls by other U.S. lawmakers for BP to suspend dividend payments. Asked if BP should do this, House of Representatives Speaker Nancy Pelosi said: "Yes, of course, and that would be their best public relations instead of taking out all these ads.
BP said in written testimony to a Senate subcommittee on Thursday that it had paid half of the 39,000 claims that had been filed so far, totalling more than $53 million.
Lawmakers will likely press BP chief executive Tony Hayward on these issues when he testifies for the first time at a congressional hearing on the spill on June 17.
BP Chief Operating Officer Doug Suttles said the company was doing everything it could to clean up the spill.
"It's very difficult for people to believe that right now, and I know that, but I would just ask, just give us a chance," he told CNN. "We've got to get this job done. We've got to get this well killed."
BP's latest effort to contain the spill involves placing a containment cap with a seal on a deep-sea pipe from which the oil is gushing into the Gulf of Mexico.
It said on Thursday the cap system had collected 15,800 barrels (660,000 gallons/2,500,000 litres) in the previous 24-hour period. The cumulative total since the system was installed last week has reached 73,324 barrels (3,080,000 gallons/11,660,000 litres), BP said.
(Additional reporting by Adrian Croft in Kabul, Alex Chambers in London, Matt Daily in New York, Ed Stoddard in Dallas, Jeremy Pelofsky and Tom Dogget in Washington, Doris Frankel in Chicago, Anna Driver in Louisiana, Michael Peltier in Pensacola Beach, Florida; writing by Ross Colvin; Editing by Will Dunham and Frances Kerry)
