UPDATE 1-New Orleans evacuation may start early Sunday-mayor

NEW ORLEANS, Aug 30 (Reuters) - City officials will order a mandatory evacuation of New Orleans starting early on Sunday if Hurricane Gustav holds to its current course, New Orleans Mayor Ray Nagin said on Saturday.

"If it continues on its current path we will start the mandatory evacuation process first thing in the morning at 8 a.m. (1300 GMT)," Nagin told reporters at City Hall. "We will make the call for the definitive mandatory evacuation."

Hurricane Gustav strengthened into a dangerous Category 4 storm on Saturday with winds of 145 mph (230 kph) as it surged toward western Cuba, the U.S. National Hurricane Center said.

Not since Hurricane Katrina in 2005 and Hurricane Rita that followed in its wake has the city been under a mandatory evacuation order. Residents would not be physically forced to leave their homes but would have to fend for themselves without help from emergency responders if they choose to stay.

Six low-lying parishes near New Orleans already have issued their own mandatory evacuation orders effective on Saturday, and Nagin said he could issue a decision for the city itself at a news conference scheduled for 7 p.m. (0000 GMT) on Saturday.

So far, city officials have evacuated 1,200 people by bus and 1,500 people by train, Nagin said. About 20,000 residents have registered with the city to be evacuated from 17 pick-up points across the city, he said. (Reporting by Kathy Finn; Editing by Bill Trott)