"The eye and the intense inner core is expected to pass near Dominica in the next few hours," the Miami-based NHC said in its 2100 GMT (2:30 am IST) bulletin.
Maria, coming two weeks after Hurricane Irma cut a path of destruction through the Caribbean, was 70 kilometres southeast of the French-speaking island of about 72,000 people, and 35 miles northeast of the French island of Martinique.
Maria was packing winds of 130 miles per hour and was now "an extremely dangerous Category Four hurricane," the NHC said.