Reports suggest Barack Obama 'won't stand in way' of bid as UK oil firm looks to sell assets to survive

BP was at the centre of fresh takeover speculation after weekend reports suggested the Obama administration has told ExxonMobil – the world's largest oil firm – that it would not stand in the way of a takeover bid for the stricken British rival.

Before the Gulf of Mexico oil spill BP was Britain's biggest company with a stock market value of £121bn. Since then more than £50bn has been wiped off its share value and a number of potential bidders are rumoured to be circling to take advantage of its weakened state.

Oil industry sources were quoted as saying that ExxonMobil had been given a green light by the US government to "take a look" at BP. A merger would create a group with a stock market value of $400bn (£265bn). Both firms refused to comment on the speculation.

BP's chief executive, Tony Hayward, is well aware of the threat of a hostile bid and last week held a series of meetings with potential "friendly" investors including the Kuwait Investment Office. A big strategic investor would make it harder for the likes of ExxonMobil or China's National Offshore Oil Company (CNOOC) to win control in a hostile takeover bid.

The Kuwaitis already have a 1.75% stake, but BP would like it to increase that to as much as 10%. Hayward is also understood to have met with another sovereign wealth fund, the Abu Dhabi Investment Authority (ADIA).

The cost of the spill to BP has already past $3.1bn (£2bn), and the company has pledged some of its assets as security to the US government while it builds up a promised $20bn compensation fund. Analysts at Goldman Sachs estimate the final bill for the disaster caused by the explosion on the Deepwater Horizon rig, which killed 11 workers, could run to $70bn.

BP has already began talks with rivals about selling off assets to help bolster its financial position. CNOOC is interested in buying the Argentinian gas businesses partly owned by BP. The UK oil firm's joint Russian venture TNK-BP has also opened talks about buying assets outside Russia.

Today Apache Corporation, the US's largest independent oil group, was named as being in exclusive talks to buy investments worth $12bn from BP, including the stake in Alaska's Prudhoe Bay, the largest oil field in North America.

Neither BP nor Apache would comment. "We've said we're going to be divesting about $10bn over the next 12 months as a result of the spill, but we have no comment on specific deals," said a BP spokesman.

BP is hoping to have some firm sales to announce before 27 July when it must release its first-half financial results and give a strategic update about the scale of liabilities faced in America.

The oil spill – and BP's handling of it – has made the firm public enemy number one in the US, with Barack Obama leading the call for blood. Such is the level of vitriol, that business groups claim American protectionism is on the rise and it is affecting other British firms. Foreign companies have already been restricted from access to US government bailout money and some important federal contracts.

This week the Washington-based Organisation for International Investment will meet a handful of British business groups including the CBI, the Chartered Institute of Taxation and Business International to discuss the rise in anti-British rhetoric and how to counter it.

· The following clarification was printed in the Guardian's Corrections and clarifications column, Monday July 19 2010. Homophone corner: "The cost of the spill to BP has already past $3.1bn …"