MIAMI (Reuters) - Tropical cyclone Sandy regained hurricane strength on Saturday after flagging wind speeds earlier in the day triggered its downgrade to a tropical storm, the U.S. National Hurricane Center said.

At 8 a.m. EDT, the Miami-based Hurricane Center said Sandy's top sustained winds were 75 miles per hour (120 km per hour), making it a weak Category 1 hurricane.

The massive storm, with a rapidly expanding wind field, was located about 335 miles southeast of Charleston, South Carolina, and moving on a north-northeast track toward its expected landfall early next week on the northeast U.S. coast.

(Reporting By Tom Brown; Editing by Vicki Allen)