"The oil is being stored and gas is being flared on the drillship Discoverer Enterprise, on the surface 5,000 feet above," BP said in a statement.

BP said the rate of oil collection continued to vary, "primarily due to the flow parameters and physical characteristics within the riser."

As an average over the May 17-23 period, BP said it collected 2,010 b/d and 10,000 Mcf/d of gas.

The company said plans continued to develop a "top kill" operation where heavy drilling fluids are injected into the well to stem the flow of oil and gas and ultimately kill the well.

"Most of the equipment is on site and preparations continue for this operation, with a view to deployment in a few days," it said, adding that the "complex operation...involves significant uncertainties and it is not possible to assure its success or to put a definite timescale on its deployment."

BP is siphoning oil from the leaking well through a riser insertion tube tool or RITT.

However, it said, "the RITT remains a new technology and both its continued operation and its effectiveness in capturing the oil and gas remain uncertain."

The US government at the weekend threatened to take over the response to the oil spill, which occurred after an explosion ripped through the Deepwater Horizon rig on April 20, killing 11 people.

"If we find that they're not doing what they're supposed to be doing, we'll push them out of the way," Interior Secretary Ken Salazar said Sunday, quoted by AFP.

--Margaret McQuaile, margaret_mcquaile@platts.com