US Vice President Joe Biden heads to the Gulf of Mexico Tuesday, as a tropical storm -- forecast to reach hurricane strength -- was likely to hamper oil spill cleanup efforts.

Biden is due to visit the New Orleans oil cleanup command center before traveling to the Florida panhandle, where the slick has forced authorities to close down some of the area's iconic white sand beaches.

The Miami-based National Hurricane Center said Tropical Storm Alex was expected to strengthen and become a hurricane, producing driving rains and blustery winds that were likely to only complicate BP's efforts to double the amount of oil captured from the ruptured well.

While cleanup crews will likely be spared a direct hit, strong winds from Alex are churning up waves large enough to make it too rough for crews to attach a third vessel to siphon oil from a containment cap some 5,000 feet (1,500 meters) below the surface.

"We're going to have to stop preparations for the Helix Producer," said US Coast Guard Admiral Thad Allen, who is overseeing the response efforts. He was referring to a vessel that was set to increase the capacity to gather the gushing oil to between 40,000 and 50,000 barrels per day by early July.

The current containment system is capturing nearly 25,000 of the estimated 30,000 to 60,000 barrels of crude spewing out of the ruptured well every day.

Even the threat of gale force winds -- upward of 45 miles (72 kilometers) per hour -- will suffice to force drilling and containment ships to withdraw from the spill site some 52 miles (83 km) off the coast of Louisiana, Allen told reporters on Monday.

Evacuations must begin 120 hours in advance, and operations will be shut down for about two weeks to "take down the equipment, move it off to a safe place, bring it back and reestablish drilling," Allen said.

That would delay the completion of relief wells designed to permanently plug the well until September, and would drastically increase the flow of oil still gushing into the sea some 70 days after the deadly explosion on the BP-leased Deepwater Horizon drilling rig.

The rough seas could also push the oil deeper into fragile coastal wetlands and has already shifted parts of the slick closer to sensitive areas in Florida and Louisiana.

"Any kind of a surge or a storm would obviously exacerbate the oil further into marshes, which would cause problems, and we're going to face that potential throughout the hurricane season," Allen said.

On its current path Alex likely will make landfall just south of the US-Mexico border either late Wednesday or early Thursday. Authorities have already issued hurricane warnings in Texas and northeastern Mexico.

At 1200 GMT, the US National Hurricane Center said Alex was picking up speed as it moved in a north-northwesterly direction at about 12 miles (19 kilometers) per hour.

The storm was about 380 miles (540 kilometers) southeast of Brownsville Texas, packing maximum sustained winds of 70 miles (110 kilometers) per hour.

And even though Alex is currently churning far from the spill area, tropical storm force winds currently "extend outward up to 105 miles (165 kilometers)" to the northeast from the storm center, the National Hurricane Center said.

The storm earlier dumped heavy rains across the Yucatan peninsula, having killed at least 10 people in Nicaragua, Guatemala and El Salvador.

Meanwhile, a frustrated former US president Bill Clinton interviewed on CNN said blowing up the well "may become necessary" and expressed concern about the ultimate success of the two relief wells currently being drilled.

"This is a geological monster," Clinton said.

"You could stop that well, but what else might you do that might upset the ecostructure of the Gulf?"

But BP vice president Kent Wells said the energy giant has a "high degree of confidence in the relief wells."

The first well, which stretches over 16,700 feet (5,090 meters), is now only 20 horizontal feet (six meters) away from the original well, Wells told reporters.

Engineers will drill parallel to the original well for about another 1,000 feet (305 meters) before trying to cut into it and block the flow of oil.

"I'm really confident in the team's chance of being successful here," Wells said.

BP earlier raised its costs over the oil spill to 2.65 billion dollars, an increase of about 300 million dollars over the weekend that means the energy firm is now forking out about four million dollars an hour.

The firm was also forced to deny reports its chief executive Tony Hayward was set to resign after weeks of taking flak for a string of gaffes and insensitive remarks about the disaster.

burs-sg/mac