(Updates with storm weakening, position)

MIAMI, Oct 17 (Reuters) - Omar lost hurricane strength on Friday, weakening to a tropical storm in the Atlantic Ocean and posing no threat to land after causing little damage this week in the northern Caribbean.

The 15th storm of a busy Atlantic hurricane season, Omar had strengthened briefly to a hurricane after moving past the U.S. and British Virgin Islands, the Dutch/French island of St. Martin and other small Caribbean nations and territories.

But the U.S. National Hurricane Center said its sustained winds had weakened to near 65 miles per hour (100 km per hour) as it moved over colder sea and it is expect to lose more strength.

Omar was about 705 (1,135) east of Bermuda and its forecast track had it heading in the general direction of Portugal's Azores Islands. Forecasters say long-range predictions have large margins of error.

Omar roared through the northern Caribbean as a powerful Category 3 hurricane with winds of 125 mph (200 kph) late Wednesday and early Thursday but made a direct hit only on a tiny, uninhabited island in the middle of the Anegada Passage.

It sank boats in harbors and knocked down trees and utility poles on a number of islands, but caused little serious damage, according to officials in the region. (Reporting by Jim Loney)

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