Crews finishing work meant to forever stop oil from leaking from a blown-out undersea well into the Gulf may have one more hurdle to overcome: the weather.

The National Hurricane Center is watching a cluster of thunderstorms in the far eastern Gulf of Mexico that forecasters say may pass near the oil spill site, just as BP drills the final 100 feet of a relief well it hopes - if the weather holds up - will intersect with the broken one as early as Friday.

The weather system could blow into a tropical storm, but forecasters don't think it'll turn into a hurricane, and BP hasn't made plans to suspend drilling.

"We are keeping a very close eye on the weather and will adjust if necessary," BP spokesman John Curry said Monday.

Finishing the new well and sealing the broken one with mud and cement should be the final act of the three-month oil spill drama that has upended the lives of fishermen and others along the Gulf Coast.

One man will guide a drill more than two miles beneath the seafloor and three miles from the surface, trying to hit a target less than half the size of a dartboard. The drill is about as wide as a grapefruit.

"It's like being in a hot air balloon 18,000 feet up and hitting a salad plate on your front lawn," said Eric Smith, associate director of the Tulane Energy Institute.

But the man BP has picked to finish the job, John Wright, has hit the mark every time, capping wells across the world in four decades of work.

"Out of 40 relief wells that I've drilled, we've never missed yet. I've got high confidence we will take care of this problem as soon as we can get there," Wright said in a June video put out by BP.

If Wright hits the mark, engineers will perform a "bottom kill" by pouring in mud and cement to permanently seal the blown-out well that's spewed an estimated 207 million gallons since April.

If he misses, engineers will pull the drill bit up, pour concrete in the off-track hole and then try again.

A "static kill" last week pushed mud and cement into the top of the crippled well, leaving very little chance oil could leak into the Gulf again, officials said.

The government's point man for the spill, retired Coast Guard

Adm. Thad Allen, is planning a three-day trip to Louisiana,

Mississippi and Alabama this week to talk with local officials about how to speed up cleanup as the peak of hurricane season approaches.

Oil spill costs continue to mount for BP. The oil giant announced Monday it has spent $6.1 billion responding to the spill since the April 20 explosion on the Deepwater Horizon killed 11 workers, sending the rig to the bottom of the sea and oil spewing 5,000 feet underwater.

Also, the Justice Department and BP announced they have finished negotiations to implement a $20 billion fund for victims of the Gulf oil spill and that BP has made a $3 billion initial deposit.