Vessels operate at the site of the Deepwater Horizon oil spill in the Gulf of Mexico on July 17, 2010. (Dave Martin/Associated Press)

Bad weather in the Gulf of Mexico could delay BP's efforts to permanently plug a blown-out well, federal officials say.

Retired U.S. Coast Guard admiral Thad Allen said Wednesday that ships would have to leave the area around the damaged well if a major storm moves into the area around the spill site.

The U.S. National Hurricane Center has said a storm headed toward Florida could strengthen in the coming days. There is a 60 per cent chance it could develop into a tropical storm by Friday.

Federal officials and BP representatives are monitoring the weather as they continue integrity tests on a containment cap that has temporarily stemmed the flow of oil into the Gulf.

Relief tunnel efforts continue

BP said Wednesday morning that integrity tests are ongoing and the well is still closed, with "no oil flowing into the Gulf."

Allen granted BP permission Tuesday to keep the valves on the custom-built containment cap closed and extend the integrity tests for another 24 hours. Scientists are monitoring the tests to determine if the cap is displacing pressure and causing leaks underground.

Meanwhile, work continues on relief wells that could permanently halt the flow of oil. The relief tunnel could reach BP's broken well by the weekend, meaning the gusher could be snuffed for good within two weeks, The Associated Press reported.

BP vice-president Kent Wells has said crews hope to drill sideways into the blown-out well and intercept it at the end of July.

After that is done, crews will begin the kill procedure, pumping mud and cement into the hole 1.6 kilometres below the water's surface to seal it. BP said that could take anywhere from five days to a couple of weeks to complete.

"Everything's looking good," Wells said. "The relief well is exactly where we want it. It's pointed in the right direction, and so we're feeling good about that."

Engineers are also considering shooting drilling mud down through the cap to increase the chances that the attempt to plug the well succeeds.

BP denies CEO stepping down

BP is denying a British newspaper report that suggests CEO Tony Hayward could step down within the next 10 weeks.

BP CEO Tony Hayward delivers his opening statement about the BP oil spill in the Gulf of Mexico at the House energy and commerce committee in Washington on June 17, 2010. (Reuters)

Citing sources close to BP, the Times newspaper in London said Hayward is expected to step down by Oct. 1, provided the blown-out well in the Gulf of Mexico is permanently sealed.

Robert Dudley, an American executive who assumed responsibility for the Gulf Coast Restoration Organization in late June, is "widely viewed as the front-runner" to replace Hayward, the Times reported.

BP spokeswoman Sheila Williams denied the report, saying, "Tony is leading the company in a strong and robust way and has the support of the board."

Hayward, 53, has faced criticism for his response to the Gulf oil spill and for comments he made during the environmental crisis, most notably that he wanted his "life back."

Hayward has not commented on the report.

The BP-leased Deepwater Horizon rig exploded April 20, killing 11 workers and touching off one of the worst U.S. environmental crises. BP said the cost of dealing with the spill has now reached nearly $4 billion.

BP said Tuesday it is selling properties in Alberta and British Columbia worth $3.25 billion US to the Apache Corporation to help pay for the cleanup and to cover compensation claims from the Gulf spill. The sale is part of a $7-billion asset deal with Apache.

With files from The Associated Press