A hurricane warning was posted for Jamaica and parts of Cuba as Sandy, with maximum sustained winds of 60 mph, was about 195 miles south of Kingston, moving north-northeast at 10 mph, the National Hurricane Center in Miami said in its 11 p.m. EDT advisory.
A tropical storm watch also is in effect for Haiti and the Bahamas.
Sandy was expected to maintain a north-to-northeast motion with some increase in forward speed for the next couple of days, forecasters said. On its forecast track, the center of Sandy will move near or over Jamaica Wednesday and approach eastern Cuba Wednesday night.
Sandy is expected to reach hurricane strength when it approaches Jamaica Wednesday, the hurricane center said.
Tropical storm-force winds extended outward from Sandy's center up to 140 miles.
Sandy is expected to produce 6-12 inches of rain across Jamaica, Haiti, the Dominican Republic and eastern Cuba, with isolated amounts of up to 20 inches possible. The rain may produce life-threatening flash floods and mudslides.
Meanwhile, Tropical Storm Tony formed about 1,505 miles west-southwest of the Azores and was moving northeast at 12 miles per hour. Maximum sustained winds were 40 mph, and no coastal watches or warnings were in effect.