BP Plc (BP.L) (BP.N) could begin a so-called "static kill" to plug its blown-out Gulf of Mexico oil well by this weekend if bad weather does not force a delay, the top U.S. official overseeing the spill response said on Wednesday.

Retired Coast Guard Admiral Thad Allen said at a briefing that if he approves the effort, bp could begin pumping heavy drilling fluid and cement into the stricken Macondo well from the top.

The static kill effort is intended to complement BP's ongoing effort to use a relief well to permanently plug the well a mile (1.6 km) under the ocean surface.

Kent Wells, BP's senior vice president of exploration and production, said in a separate briefing that the static kill might stop the leak on its own.

"We will continue on with the relief well. Even if the static kill kills the well, we will confirm that with the relief well," he said.

This would mark BP's latest in a string of efforts to tackle the massive oil leak that began three months ago.

The relief well remains on track to intercept the Macondo well by the end of July and kill the leak by mid-August, though bad weather could cause a delay, Wells said.

Allen and Wells said the relief well needs one last set of piping, or casing, cemented in place to hold it open before a drill bit can bore into the Macondo well near its bottom 13,000 feet (2.4 miles/4 km) below the seabed, Allen said.

"Once the casing is in place, the static kill can proceed by this weekend," Allen said.

Wells said bp needs two to four days to position the casing and cement it in place. Then the static kill could take place in one day, he said.

BAD WEATHER

In the meantime, bp stopped work on the relief well while officials watch a northern Caribbean weather system. The system could move into the Gulf and force the company to delay its work by up to 14 days if all vessels must evacuate, Allen said.

"Any operations out there would have to be suspended whether it's containment or the relief well" if the weather deteriorates, Allen said during a briefing in Washington.

"They're starting to get choppy out there now, we're looking at 4- to 6-foot seas (1.2 to 1.8 metres)," he said.

The U.S. National Hurricane Center said on Wednesday the system had a 50 percent chance of strengthening into a tropical depression in the next 48 hours, down from a 60 percent chance.

Allen said bp is holding off on putting the last bit of casing in the relief well "pending the decision of whether or not we can remain on scene."

Wells had earlier explained that the static kill would work much like BP's failed "top kill" effort in May with one critical difference -- this time, the well is capped.

Both involve pumping mud and cement into the well through a hose connected to a failed blowout preventer at the seabed. But mud shot out the top of the uncapped well during the top kill.

BP placed a tight-fitting containment cap over the ruptured well last week that on July 15 stopped -- at least temporarily -- the flow of oil into the sea for the first time since the April accident.

The cap on the wellhead should mean that mud would not escape, Wells said.

The cap remains sealed amid an ongoing test of pressure within the well to determine if it is intact after the April 20 blowout, Allen said.

He added that a weather-related vessel evacuation would include ships that operate underwater robots, interrupting live feeds of seabed operations for three to four days.