ROSEAU, Dominica (AP) — Leaders across much of the Caribbean closed schools and government offices on Wednesday as Tropical Storm Isaac swept toward the region, and the U.S. military postponed hearings for Sept. 11 prisoners ahead of a storm that could sweep across Cuba and perhaps eventually menace Florida as a hurricane.

The storm was 75 miles (120 kilometers) east-northeast of Dominica early Wednesday afternoon, with maximum sustained winds of 45 mph (75 kph). Isaac was moving west at 21 mph (33 kph) and is expected to become a hurricane by Thursday, according to the U.S. National Hurricane Center.

Dominica Prime Minister Roosevelt Skerrit urged people to stay home from work on Wednesday.

"I want us all to be safe," he said. "I don't want lives to be lost."

Military authorities in Guantanamo Bay, Cuba, canceled several days of pretrial hearings in the case of five prisoners charged in the Sept. 11 attacks. They also planned to evacuate about 200 people, including legal teams and relatives of Sept. 11 victims.

Isaac also posed a possible threat to Florida during next week's Republican National Convention in Tampa, according to forecasters, though the hurricane's track was uncertain.

Tess Hunneybell, owner of Manico River Eco Resort, which features luxury treehouses perched in the foothills of Dominica's Morne Aux Diables volcano, said there was still barely a breeze Wednesday afternoon as dark clouds gathered over the sea.

"Right now, it's definitely the calm before the storm. But we can see the clouds coming this way," Hunneybell said.

She and others wrapped the treehouses in tarpaulin and nailed shut louvre doors in anticipation of Isaac. There were no guests as flights to the jagged, densely forested island had been suspended.

In Puerto Rico, Gov. Luis Fortuno declared a state of emergency and activated the National Guard. He also canceled classes and closed government agencies on Wednesday. Federal officials also closed the popular San Felipe del Morro castle in Old San Juan. The storm was expected to pass just south of Puerto Rico on Thursday.

The U.S. Coast Guard closed all ports in Puerto Rico and the U.S. Virgin Islands to incoming commercial ships and warned that all commercial vessels bigger than 200 gross tons must leave or obtain permission to remain in port.

The U.S. Virgin Islands commissioner of public works, Darryl Smalls, said crews distributed sandbags to residents in St. Croix, where schools and government offices will close on Thursday. St. Kitts also announced similar closures for Wednesday.

Liat airline and American Eagle canceled flights to islands including Dominica, the U.S. Virgin Islands, Guadeloupe and Martinique.

The storm's center was expected to move over the Leeward Islands on Wednesday evening, and forecasters said it is expected to hit the Dominican Republic as a hurricane early Friday. It is then expected to hit Cuba as a tropical storm.

In the island of Vieques, which lies just east of Puerto Rico, people prepared for the government to temporarily shut off the power.

Glenn Curry, an owner of Bananas Guesthouse, said he closed the restaurant and will move guests to a higher floor.

"I don't think this is going to be a major storm, but it's going to be noisy and unpleasant for a few hours," he said.

Meanwhile, the general manager of the Hilton Golf & Casino Resort in the southern city of Ponce, Puerto Rico's second largest city, said he has warned guests about the impending storm.

"We expect bad weather, rain, wind, but nothing to the extent of danger," said Gunther Mainka.

He said the hotel prepares for storms in July, including trimming the numerous palm trees that surround the resort.

"They get a big haircut," he said. "All the loose branches go down, all the coconuts go down."


Associated Press reporters Danica Coto in San Juan, Puerto Rico, David McFadden in Kingston, Jamaica, contributed to this report.