SAN JUAN, Puerto Rico -- Hurricane Irma could threaten islands at the eastern end of the Caribbean Sea on Tuesday, just a week after Hurricane Harvey ravaged South Texas.

Hurricane watches were posted for Antigua and Barbuda, Anguilla, Montserrat, St. Kitts and Nevis, St. Martin, Guadeloupe and the British Virgin Islands.

The U.S. National Hurricane Center said the center of the storm could near that region late Tuesday. It said islands farther north, including the U.S. Virgin Islands and Puerto Rico, should monitor the progress of the storm.

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Irma is a Category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale, the center said in an advisory early Monday, adding that some strengthening is expected over the next two days. The center said Irma had maximum sustained winds of almost 115 mph. It was centered about 680 miles east of the Leeward Islands, moving west-southwest at 14 mph.

Here are the 11 pm AST key messages on #Irma.:https://t.co/zSNegSYJaF pic.twitter.com/QsLJvHSUNY — NHC Atlantic Ops (@NHC_Atlantic) September 4, 2017

Irma formed on the heels of Harvey, which struck the Gulf Coast of Texas on Aug. 26. Thousands have been displaced by the storm due to torrential rain and flooding. Texas Gov. Greg Abbott estimates Harvey caused up to $180 billion in damage.

A "forecast cone" showing the probable path of Hurricane Irma, as of 2 a.m. ET on Mon., September 4, 2017; "M" stands for Major Hurricane National Hurricane Center

Long-range forecasts indicated Irma likely would curve to the northwest beginning late Monday and skirt to the north of those islands on a path that could potentially take it to the U.S. East Coast, but it was too early to make a definitive prediction.

Antigua's prime minister, Gaston Browne, urged people to take preventative measures in case Irma should hit, including cleaning drains and removing objects that could be sent airborne by high winds.

Workers began pruning trees and shrubs to reduce chances for branches to tear down power and phone lines.

"The passage of a hurricane is not a matter to be taken lightly, but we must not panic," Browne said in a statement.

The Antigua and Barbuda weather service said Irma was expected to bring heavy rains, rough surf and high winds to islands along the northern edge of the Antilles.

Puerto Rico's governor, Ricard Rossello, said government agencies in the U.S. territory were prepared to deal with any emergencies caused by the storm.

"We have established protocols for the safety of all," he said at a news conference, while he also urged islanders to take precautions.

In the Dominican Republic, Public Works Minister Gonzalo Castillo said workers there were clear away road works and also clean out blockages of sewer drains. He said President Danilo Medina would lead a meeting with emergencies agencies on Monday to discuss storm preparations.