BP is asked for advance notice of dealings by US
The US government has asked BP to tell it of any major asset sales or merger deals in advance, as it continues to keep a close eye on the oil giant.
The highly unusual request came in a letter from the US Department of Justice dated 23 June.
BP told the BBC it had yet to respond to the letter.
The company is facing massive clean-up costs and compensation claims as a result of the Gulf of Mexico oil leak, which began in April.
The US government has been highly critical of BP's handling of the oil leak.
Congressmen have accused chief executive Tony Hayward of not taking responsibility, while questioning him about alleged cost-cutting measures that could have contributed to the leak.
In its latest update, BP said the oil leak had now cost it $3.12bn (£2bn), though the total cost is forecast by analysts to be tens of billions of dollars.
As a result, it has said it will look at selling some assets and attracting new investment.
On Wednesday, Mr Hayward was visiting Abu Dhabi, with media reports speculating he was in the region to entice wealthy investors.
BP said Mr Hayward's visit was routine.
There has been a great deal of speculation in recent days about potential investors in BP, including the Kuwaiti Investment Authority, China's PetroChina and the US oil giant Exxon Mobil.
These reports, as well as statements from BP saying the company had no plans to issue new shares, have helped the company's share price to rally this week.
On Wednesday, it rose a further 5%.
But despite the bounce, BP's shares have almost halved in value since an explosion on the Deepwater Horizon oil rig triggered the leak on 20 April.
Oil is continuing to spill into the Gulf and BP has said two relief wells being drilled to stop the leak are on course for completion by August.