(Adds forecast details, changes dateline from Washington)

MIAMI, Sept 2 (Reuters) - A new tropical depression formed in the far eastern Atlantic Ocean south of the Cape Verde Islands and was expected to become a tropical storm later on Tuesday, the U.S. National Hurricane Center said.

The depression, which will be called Tropical Storm Josephine once its maximum sustained winds reach 39 miles per hour (64 kph), was located 170 miles (270 km) southeast of the Cape Verde Islands, the Miami-based center said.

It was the 10th tropical depression of this year's busy Atlantic hurricane season.

The center said the cyclone, moving in a northwesterly direction, was expected to steadily intensify over the next 24 hours and could become a hurricane within three days.

As Hurricane Gustav was downgraded to a tropical depression after slamming the U.S. Gulf coast, Hurricane Hanna is threatening the U.S. east coast from Florida to the Carolinas, and Tropical Storm Ike formed in the Atlantic Ocean.

Hanna, a category 1 hurricane with maximum sustained winds of 80 mph (130 kph), was expected to strengthen on Wednesday when it was likely to become a category 2, the center said.

Hanna was dumping heavy rain on the southeastern Bahamas, the Turks and Caicos Islands, and Haiti, the NHC said, adding it could cause life-threatening mudslides and flash floods on the north side of the island of Hispaniola, shared by Haiti and the Dominican Republic. (Reporting by Sandra Maler; Editing by Giles Elgood)

AlertNet news is provided by