Forecasters say Tropical Storm Isaac continues to move west toward the Caribbean on a track that could possibly take it toward Florida, where the Republican National Convention is to be held next week.

The National Hurricane Center said Isaac had top sustained winds near 40 mph (64 kph) at 11 p.m. EDT Tuesday and was expected to strengthen. It was 390 miles (628 kilometers) east of Guadeloupe and heading west near 18 mph (29 kph).

Tropical storm warnings were issued Tuesday for Puerto Rico, the U.S. and British Virgin Islands and a swath of islands across the Caribbean including Martinique, Dominica, Guadeloupe, St. Martin, St. Kitts, Nevis, Antigua, Barbuda, Montserrat, Anguilla, Saba, St. Eustatius, St. Maarten, Culebra and Vieques.

It's too soon to gauge the storm's exact path. Some computer models forecast Isaac to head toward Cuba and then Florida, while others suggest a sharp northern turn in coming days near Puerto Rico before entering the open Atlantic.