NEW ORLEANS (AFP)--U.S. officials were Wednesday anxiously eyeing a patch of bad weather building in the Caribbean, just as they approach the end game in efforts to seal for good a blown-out well. The weather system, if it strengthens as it heads into the Gulf of Mexico, could delay relief efforts for up to 10 to 14 days, said retired Coast Guard Adm. Thad Allen, who is overseeing the federal response to the spill. U.S. weather experts were Wednesday flying a plane over a depression forming near the Gulf to try to determine if it was going to build into a major storm and what its path might be, Allen said. Depending on the results, U.S. officials may have to start evacuation orders for hundreds of ships and engineers feverishly trying to complete a relief well being drilled deep under the seabed to intercept with the damaged wellbore. "If we have to evacuate the area ... we could be looking in 10 to 14 day gaps in our lines of operation," said Allen. BP PLC (BP, BP.LN) has been frantically working to seal the well as hurricane season gets fully under way. The news that a storm may be forming, after a run of good weather, is frustrating given that BP could begin an operation to seal the well by drowning it with mud as early as this weekend. If the weather shows no sign of hampering their work, Allen said a few steps had to be completed first, including completing the casing around the relief well, and securing the wellbore. "At that point we could proceed to the static kill ... if that is approved," Allen said, adding that the operation to inject mud and cement through a cap on top of the well could start as early as this weekend. BP would then also move to pump extra mud via the relief well into the bottom of the damaged well, in the hopes of finally choking off the oil bubbling up from the subsea reservoir. Allen said experts and scientists were poring over the weather data as well as results from six days of painstaking tests on the damaged well and would decide on the next steps later Wednesday. The National Hurricane Center, in its 8 a.m. advisory, said the weather system, which now is moving across the island of Hispaniola, has become less organized, but has a 60% chance of developing into a tropical cyclone over the next 48 hours. (END) Dow Jones Newswires July 21, 2010 12:25 ET (16:25 GMT)