Katia had sustained winds of 70 miles per hour and would become the second hurricane of the June-through-November Atlantic hurricane season if winds reach 74 mph, the U.S. National Hurricane Center said.
The Miami-based center said Katia was forecast to become a "major" hurricane with winds over 111 mph on Sunday, but it was still too early to tell whether it would threaten land.
At 5 p.m. (2100 GMT), Katia was about 1,285 miles east of the Caribbean's Leeward Islands. It was moving rapidly west-northwest and was forecast to turn northwest in a couple of days on a course that would keep it away from the Caribbean islands.
Hurricane Irene rampaged up the U.S. East Coast over the weekend and authorities on the U.S. Atlantic seaboard are keeping an eye on Katia to see which path it takes.
Long-range computer models, which can be off by hundreds of miles, show Katia nearing the mid-Atlantic island of Bermuda in about a week. Several models turned it north, away from the U.S. East Coast.
The Atlantic hurricane season typically brings 11 or 12 named storms. Katia is already the 11th, and with half of the season still ahead, it is shaping up to be the unusually busy year that was predicted.
Energy companies with oil and natural gas operations in the Gulf of Mexico were keeping watch on a mass of thunderstorms over the northwest Caribbean Sea and eastern Gulf.
Forecasters said there was a "medium" chance of it developing into a tropical cyclone in the next two days.
BP on Wednesday became the first major oil producer to say it was already evacuating some workers from offshore platforms in the Gulf because of the weather system, which would be dubbed Lee if it becomes a named storm.
Royal Dutch Shell said later it too was preparing to evacuate some workers, while other companies said they were monitoring the system closely.