Hurricane Sandy is barreling toward the tri-state region with heavy rain and wind gusts that forced officials to call for evacuations, shut down mass transit and prepare for the worst in advance of the massive storm that is set to make landfall in New Jersey early Tuesday.

New York City Mayor Michael Bloomberg ordered a mandatory evacuation of low-lying areas in New York City and said the city's school system would be closed Monday. Bus, subway and commuter rail service in the city was halted in advance of the massive storm expected to hit the eastern third of the United States.

The mayor called for a mandatory evacuation of residents living in Zone-A by 7 p.m. on Sunday.

Low-lying areas in the evacuation zone include Coney Island, Red Hook, and other areas around the East River in Brooklyn, the Rockaways, Broad Channel, the Staten Island coast line, City Island, Battery Park City, stretches of the West Side waterfront and parts of the Lower East Side and the East Village.

About 370,000 people live in these evacuation zones.

The New York City subway system will begin to curtail service after 7 p.m., and the New York City bus system within the following two hours. Metro-North Railroad and the Long Island Rail Road will start their final trains by 7 p.m. Subway and railway stations will be closed after the last trains.

When asked it it would have been better to call for an evacuation on Saturday, the mayor said "absolutely not": "We’re not here to inconvenience anyone," he said. "We’re here to protect safety. If conditions warrant we’ll make those decisions."

Major bridges will be closed on a "case by case" basis or when the wind reaches speeds above 60 mph, New York Governor Andrew Cuomo said.

Officials said it was unclear when transit would be up and running again after the shut down. Service should be able to return 12 hours after the storm. 

When the MTA halted service during Hurricane Irene in August 2011 it was the first such weather-related shutdown in the agency's history.

In New Jersey, Governor Chris Christie issued mandatory evacuations for the state's barrier islands. NJ Transit will implement a system-wide shut down of its services beginning Sunday afternoon. State offices will also be closed.

The head of New Jersey's Board of Public Utilities says residents should brace themselves for widespread and prolonged power outages. Gov. Christie asked residents for patience. “Be prepared...we’re not going to get power people out until after [the storm is over]," he said

Hurricane Sandy has been making its way toward the eastern seaboard, and could combine with a storm system from the west and cold air from Canada to bring heavy rains and strong winds Monday and Tuesday. The severity of this rare convergence was unclear Saturday.

On Long Island, officials are preparing for what they call an "unprecedented" storm.  There are mandatory evacuations for Long Island's barrier islands, a voluntary evacuation for known flood zones on Long Island.

Suffolk County Transit will continue running buses until further notice. Suffolk County parks are closing and campers are being forced to leave.

Hurricane Sandy is expected to hit the central New Jersey coastline on Monday. It’s poised to meet two other powerful winter storms, and experts says it doesn’t matter how strong Sandy is when it hits land: The rare hybrid storm that follows will cause havoc over 800 miles from the East Coast to the Great Lakes.

"This is not a coastal threat alone," said Craig Fugate, director of the Federal Emergency Management Agency. "This is a very large area."

President Barack Obama signed a New York emergency declaration and ordered federal aid to help state and local response to the storm. He was also monitoring the storm and working with state and locals governments to make sure they get the resources needed to prepare, administration officials said.

States of emergency have been declared in New York, New Jersey and Connecticut.

New Jersey Governor Chris Christie called for mandatory evacuations of barrier islands from Sandy Hook to Cape May and for Atlantic City casinos by Sunday at 4 p.m. Residents lined up Sunday at the Atlantic City Convention Center to board buses to shelters on the mainland. Officials say the busing will continue until winds reach tropical storm strength. After that, anyone who couldn't get on a bus may be forced to stay in "last resort" shelters that are being set up at city schools.

NJ Transit also began a gradual shutdown of service, with service expected to be suspended by 2 a.m. Monday.

Amtrak has begun canceling train service to parts of the East Coast and canceled all trains on Monday along the Northeast Corridor. Airlines are adding Sunday flights out of New York City and Washington in preparation for Monday flight cancellations.

Coastal towns in Connecticut, such as Fairfield, Old Saybrook and East Haven, have issued mandatory evacuation for residents in beach areas.

With Scott Gurian in Long Island and the Associated Press