ORLANDO/MIAMI (REUTERS) - Hurricane Matthew, the first major hurricane threatening a direct hit on the United States in more than 10 years, closed in on Florida on Thursday (Friday Singapore time) after killing at least 339 people in Haiti on its destructive march north through the Caribbean.

Carrying extremely dangerous winds of 215 kph, the storm pounded the north-western part of the Bahamas en route to Florida's Atlantic coast, the US National Hurricane Centre (NHC) said.

Matthew's top sustained winds had dropped by Thursday night but it remained Category 4 on the five-step Saffir-Simpson scale of hurricane intensity as it neared Florida, where it could either plow inland or tear along the Atlantic coast through Friday night local time, the Miami-based centre said.

Few storms with winds as powerful as Matthew's have struck Florida, and the NHC warned of "potentially disastrous impacts." The US National Weather Service said the storm could be the most powerful to strike north-east Florida in 118 years.

Hurricane conditions were expected in parts of Florida late on Thursday or early on Friday local time and a dangerous storm surge was expected to reach up to 3.35m along the Florida coast, Mr Ed Rappaport, deputy director of the Miami-based NHC, said on CNN. "What we know is that most of the lives lost in hurricanes is due to storm surge," he said.

Some 339 people were killed in Haiti, local officials said, and thousands were displaced after the storm flattened homes, uprooted trees and inundated neighborhoods earlier in the week. Four people were killed in the Dominican Republic, which neighbours Haiti.

Damage and potential casualties in the Bahamas were still unclear as the storm passed near the capital Nassau on Thursday and then out over the western end of Grand Bahama Island.

It was too soon to predict where Matthew might do the most of its damage in the United States, but the NHC's hurricane warning extended up the Atlantic coast from southern Florida through Georgia and into South Carolina. More than 12 million people in the United States were under hurricane watches and warnings, according to the Weather Channel.

The last major hurricane, classified as a storm bearing sustained winds of more than 177 kph, to make landfall on US shores was Hurricane Wilma in 2005.

Mr Jeff Masters, a veteran hurricane expert, said on his Weather Underground website (www.wunderground.com) that Matthew's wind threat was especially serious at Cape Canaveral, which juts into the Atlantic off central Florida.

"If Matthew does make landfall along the Florida coast, this would be the most likely spot for it. Billions of dollars of facilities and equipment are at risk at Kennedy Space Centre and nearby bases, which have never before experienced a major hurricane," Mr Masters wrote.

NASA and the US Air Force, which operate the nation's primary space launch site at Cape Canaveral, have already taken steps to safeguard personnel and equipment.