(Reuters) - Tropical Storm Hermine was heading toward the northern Florida coast on Thursday and is expected to strengthen into a hurricane by the time it hits land, the U.S. National Hurricane Center said.

The storm was located in the Gulf of Mexico about 275 miles (440 km) west-southwest of Tampa, Florida, with maximum sustained winds of 60 miles per hour (95 kmph).

A tropical storm warning has been issued for the U.S. east coast from Marineland, Florida to South Santee River, South Carolina, the Miami-based weather forecaster said.

"On the forecast track, the center of Hermine will be near the Florida coast in the warning area tonight or early Friday," the Miami-based center said.

(Reporting by Eileen Soreng in Bengaluru, Editing by Angus MacSwan)