Published: Jul 22, 2010 11:06 AM EDT
Updated: Jul 22, 2010 8:06 AM EDT

ON THE GULF OF MEXICO (AP) - Crew members aboard dozens of ships in the Gulf of Mexico prepared Thursday to evacuate as a tropical rainstorm brewing in the Caribbean brought the deep-sea effort to plug BP's ruptured oil well to a near standstill.

Though the rough weather was hundreds of miles from the spill site and wouldn't enter the Gulf for at least a few more days, officials ordered technicians trying to plug BP's well to stand down because they needed several days to clear the area.

Anxiety built among the 75-member crew aboard the cutter Decisive, the Coast Guard's primary search and rescue vessel that would be the last of about 65 ships to leave in the event of an evacuation.

"It's a controlled chaos out there," Lt. Patrick Montgomery told an Associated Press reporter aboard the cutter heading from Pascagoula, Miss., to the spill site.

Just days before the expected completion of a relief well designed to permanently throttle the free-flowing crude, the government's spill chief said Wednesday that work was suspended.

Worse yet, retired Coast Guard Adm. Thad Allen said foul weather could require reopening the cap that has contained the oil for nearly a week, allowing oil to gush into the sea again for days while engineers wait out the storm.

"This is necessarily going to be a judgment call," said Allen, who was waiting to see how the storm developed before deciding whether to order any of the ships and crews stationed some 50 miles out in the Gulf of Mexico to head for safety.

The cluster of thunderstorms passed over Haiti and the Dominican Republic on Wednesday, and forecasters said the system would probably move into the Gulf over the weekend. They gave it a 40 percent chance of becoming a tropical depression or a tropical storm by Friday.

Crews had planned to spend Wednesday and Thursday reinforcing with cement the last few feet of the relief tunnel that will be used to pump mud into the gusher and kill it once and for all. But BP put the task on hold and instead placed a temporary plug called a storm packer deep inside the tunnel, in case it has to be abandoned until the storm passes.

"What we didn't want to do is be in the middle of an operation and potentially put the relief well at some risk," BP vice president Kent Wells said.

If the work crews are evacuated, it could be two weeks before they can resume the effort to kill the well. That would upset Bp's timetable, which called for finishing the relief tunnel by the end of July and plugging the blown-out well by early August.