* Death toll rises to at least 339 in Haiti
* Mass evacuations in four U.S. states
* Storm could hit Florida directly or brush coast (Updates with number of people killed in paragraph 1 and 7, speed of winds in paragraph 2, Obama declaring state of emergency in Georgia in paragraph 23, location of storm in paragraph 26)
By Scott Malone and Gabriel Stargardter
ORLANDO, Fla./MIAMI, Oct 6 (Reuters) - Matthew, the first major hurricane threatening a direct hit on the United States in more than 10 years, closed in on Florida on Thursday after killing at least 339 people in Haiti on its destructive march north through the Caribbean.
Carrying extremely dangerous winds of 130 mph (215 kph), the storm pounded the northwestern part of the Bahamas en route to Florida's Atlantic coast, the U.S. National Hurricane Center said.
Matthew's top sustained winds had dropped to 130 mph by Thursday night. But it remained a 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, the Miami-based center said.
Few storms with winds as powerful as Matthew's have struck Florida, and the NHC warned of "potentially disastrous impacts."
The U.S. National Weather Service said the storm could be the most powerful to strike northeast Florida in 118 years.
Hurricane conditions were expected in parts of Florida late on Thursday or early on Friday and a dangerous storm surge was expected to reach up to 11 feet (3.35 meters) along the Florida coast, 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 neighbors 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 110 mph (177 kph), to make landfall on U.S. shores was Hurricane Wilma in 2005.
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 Center and nearby bases, which have never before experienced a major hurricane," Masters wrote.
NASA and the U.S. Air Force, which operate the nation's primary space launch site at Cape Canaveral, have already taken steps to safeguard personnel and equipment.
A team of 116 employees was bunkered down inside Kennedy Space Center's Launch Control Center to ride out the hurricane.
"We've had some close calls, but as far as I know it's the first time we've had the threat of a direct hit," NASA spokesman George Diller said by email from the hurricane bunker.
Roads in Florida, Georgia and North and South Carolina were jammed, and gas stations and food stores ran out of supplies as the storm approached early on Thursday.
Florida Governor Rick Scott warned there could be "catastrophic" damage if Matthew slammed directly into the state and urged some 1.5 million people there to evacuate.
"If you're reluctant to evacuate, just think about all the people ... already killed," Scott said at a news conference. "Time is running out. This is clearly either going to have a direct hit or come right along the coast."
Scott, who activated several thousand National Guard troops to help deal with the storm, warned that millions of people were likely to be left without power.
Florida, Georgia and South Carolina opened shelters for evacuees. As of Thursday morning, more than 3,000 people were being housed in 60 shelters in Florida, Scott said.
Those three states as well as North Carolina declared states of emergency, empowering their governors to mobilize the National Guard.
President Barack Obama called the governors of the four states on Thursday to discuss preparations for the storm. He declared a state of emergency in Florida and South Carolina, a move that authorized federal agencies to coordinate disaster relief efforts. Late Thursday, Obama declared an emergency in Georgia and ordered federal aid to the state.
"Hurricane Matthew is as serious as it gets. Listen to local officials, prepare, take care of each other," Obama warned people in the path of the storm in a posting on Twitter.
Hundreds of passenger flights were canceled in south Florida, and cancellations were expected to spread north in coming days along the storm's path, airlines including American Airlines, Delta Airlines and United Airlines said.
At 11 p.m. EDT (0300 GMT), Matthew was about 125 miles (200 km) southeast of Florida's Cape Canaveral, the hurricane center said. It was heading northwest at about 13 mph (20 kph) and was expected to continue on this track through Thursday and early Friday. The center said the storm is expected to gradually weaken during the next 48 hours.
In Florida, fuel stations on Thursday afternoon posted "out of gas" signs after cars waited in long lines to fill up. At a Subco gas station in Orlando, the pumps had run dry on Wednesday.
The shop was a stopping point for coastal residents seeking shelter inland. Among them was Jonas Sylvan, 44, of Melbourne, Florida, who planned to hole up in a hotel with his wife, two daughters and dog. "We're just trying to get away from the coast," he said. "It's safer here."
Reporting by Brendan O'Brien in Milwaukee, Neil Hartnell in Nassau, Rich McKay in Atlanta, Nick Carey in Chicago, Harriet McLeod in Charleston, S.C., Doina Chiacu in Washington, Joseph Guyler Delva in Haiti, Irene Klotz and Laila Kearney; Writing by Frances Kerry and Tom Brown; Editing by Cynthia Osterman, Peter Cooney and Christian Schmollinger