MIAMI (Reuters) – Tropical Storm Chantal strengthened slightlyon Tuesday as it swept into the eastern Caribbean and moved betweenthe islands of Martinique and St. Lucia, U.S. forecasters said.

Chantal was centered about 55 miles northwest of St. Lucia, theU.S. National Hurricane Center said. The storm had top sustainedwinds of 60 mph and was speeding west-northwest at 29 mph.

Chantal, the third named storm of the 2013 Atlantic hurricaneseason, did not pose an immediate threat to U.S. oil and gasoperations in the Gulf of Mexico.

The storm is forecast to continue moving over the easternCaribbean on Tuesday on a path that would put it over Haiti and theDominican Republic on Wednesday.

Forecasters said Chantal is expected to reach near hurricanestrength as it approaches Hispaniola, the island made up of Haitiand the Dominican Republic, but remain a tropical storm.

Chantal could pose a particular threat to Haiti, the poorestcountry in the Americas which is vulnerable to flash floods andmudslides because of its near-total deforestation.

Computer forecast models show Chantal is then forecast to moveover the Bahamas, with its eye remaining well off the U.S. coastover the weekend.

In Barbados, businesses and government officers were closed onTuesday as the storm buffeted the island.

Authorities in the Dominican Republic issued a hurricane watchfor parts of the country. Tropical storm warnings were in effectfor Dominica, Martinique, Guadeloupe, Puerto Rico and the northerncoast of Haiti.

(Reporting by Kevin Gray; Editing by CynthiaOsterman)