President Barack Obama and British Prime Minister David Cameron were expected to discuss London-based BP Plc and the Gulf of Mexico oil spill on Saturday as stormy weather raised fears that clean-up operations could be disrupted.

The oil spill, the worst in U.S. history, is overshadowing the first meeting between Obama and Cameron since the prime minister took office last month, which will take place on the sidelines of the G8/G20 summit in Canada.

The British energy giant's share price is trading at 14-year lows after falling sharply again on Friday, when Cameron offered his strongest comments yet on the issue.

It is ... in all our long-term interests that there is some clarity, some finality, to all of this, so that we don't at the same time see the destruction of a company that is important for all our interests, Cameron told Canadian broadcaster CBC.

This is a vital company for all of our interests. ... BP itself wants to cap the well and clean up the spill and compensate those who have had damages, Cameron said.

Obama has been highly critical of BP while his own poll ratings have fallen, in part because of perceptions that his handling of the crisis has been too slow.

British business and shareholder groups have meanwhile clamored for Cameron to defend the company.

But Cameron insisted on Friday he believed the matter called for gentle persuasion.

This isn't an issue between Britain and America. This is about BP doing what it should, but also being treated in a way that enables it to go forward, he told reporters.

Far from the high-level talks, those involved in the clean-up and containment efforts were anxious about Saturday's formation of the first tropical storm of the 2010 Atlantic hurricane season in the western Caribbean, a development that could disrupt such operations for days or weeks.

Tropical storm Alex was located 250 miles east southeast of Chetumal, Mexico, and moving west-northwest at 8 mph. Its path would take it toward Belize and over the Yucatan Peninsula during the weekend and then into the Gulf of Mexico, where workers are battling to contain the spill, though it was too early to tell if it would affect such operations.

MOUNTING TOLL

In the Gulf, BP said its oil-capture systems collected or burned off 23,725 barrels of oil on Thursday.

U.S. Coast Guard Admiral Thad Allen, who oversees the federal relief effort, said BP was on track to nearly double its oil collection capacity next week -- weather cooperating.

The disaster is taking a mounting toll on fishing and tourist industries in the Gulf and threatens to wreak havoc on a grand scale on coastal ecosystems and wildlife.

Share losses for BP since the spill began on April 20 stand at around $100 billion, more than halving its market value prior to the disaster, as investors fret about the potential costs which include but are not limited to a $20 billion compensation fund it set up under intense political pressure.

BP has added $5 billion to its available credit to ensure it has enough money to meet the cost of the spill, according to a story on the Wall Street Journal's website.

BP stock on Friday fell more than 6 percent in London and New York and its performance early next week may hinge on what Obama and Cameron have to say after their talks.

(Additional reporting by Ernest Scheyder in Louisiana and Sinead Carew in New York; Writing by Ed Stoddard; editing by Todd Eastham)

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