MIAMI, Florida — Hurricane Dorian gained strength as it crept closer to Florida's coast on Friday, raising the risk that parts of the US state will be hit by strong winds, a storm surge and heavy rain for a prolonged period after it makes landfall early next week.

The Miami-based National Hurricane Center (NHC) issued a hurricane watch for northwestern Bahamas, and said Dorian was likely to remain an extremely dangerous hurricane as it approaches Florida through the weekend.

"The biggest concern will be Dorian's slow motion when it is near Florida, placing some areas of the state at an increasing risk of a prolonged, drawn-out event of strong winds, dangerous storm surge, and heavy rainfall," the center said.

The storm began on Friday over the Atlantic as a Category 2 but was already expected to be classified a Category 3 later in the day, with sustained winds of at least 110 miles per hour (175 km per hour).

The entire state of Florida was under a declaration of emergency, and Governor Ron DeSantis has activated 2,500 National Guard troops, with another 1,500 on standby.

Forecasters predicted the storm would grow more ferocious as it gained fuel from the warm waters off Florida, slamming into the state late on Monday or early Tuesday. Tropical storm winds could be felt in Florida as soon as Saturday.

No evacuations were ordered as of early Friday, but many were expected as the storm's path becomes clearer before it makes landfall.

If, as expected, the storm reaches Category 4 over the weekend, its winds will blow at more than 130 mph (210 kph). There was concern that it could slow from its current 12-mph (9-kph) march across the map, giving it more time to draw fuel from warm seas.

Recent NHC weather models show Dorian smacking into the center of Florida. It was trending northwest in the latest advisory issued at 8 a.m. EDT (1200 GMT) on Friday.

The storm could roll inland toward Orlando on Tuesday or early Wednesday, weakening as it moves away from the sea. Other NHC weather models show it tracking south toward Miami before hitting the peninsula, or heading north to the Georgia coast.

Along with the dangerous winds, the storm was expected to drop 6 to 12 inches (15 to 30 cm) of rain on the coastal United States, with some areas getting as much as 15 inches (38 cm).

"This rainfall may cause life-threatening flash floods," NHC forecasters said.

President Donald Trump on Thursday canceled a planned weekend trip to Poland, sending Vice President Mike Pence in his place, so he can make sure resources are properly directed for the storm.

"Now it's looking like it could be an absolute monster," Trump said in a video posted on Twitter, adding that food and water were being shipped to Florida.

Governor DeSantis said Floridians need to take the storm seriously.

"Hurricane #Dorian is moving slowly & gaining strength," DeSantis wrote on Twitter. "Now is the time to get prepared & have a plan."

Georgia Governor Brian Kemp declared a state of emergency in 12 counties to assist with storm readiness, response and recovery.

Angela Johnson, a 39-year-old bar manager in South Florida, said on Thursday, "We're worried. This is not looking good for us."

"We woke up a lot more scared than we went to bed last night, and the news is not getting any better," said Johnson, who manages Coconuts On The Beach, a bar and restaurant on the surfing beach in the town of Cocoa Beach.

Officials were making piles of sand available for Cocoa Beach residents to fill sandbags starting on Friday.

Dorian could churn across dozens of launchpads owned by the National Aeronautics and Space Administration (NASA), the Air Force and companies such as Elon Musk's SpaceX and Jeff Bezos' Blue Origin. — Reuters