US President Barack Obama on Monday noon warned Americans that the approaching Hurricane Sandy was a "big and powerful" storm with slow moving process and wide swath, and urged residents across impacted area to follow the instructions of local authorities.

Obama made the scheduled statement at the White House at 12:45 p.m. (1645 GMT) after having a briefing about the approaching deadly storm.

"This is going to be a big and powerful storm and all across the Eastern Seaboard I think everybody is taking the appropriate preparations," said Obama during the televised statement.

Obama said he was confident that state and federal governments have done all they can to prepare for the superstorm which is anticipated to make its landfall on Monday evening.

Obama said the storm will affect millions of people and hence the most important message to the public is "please listen to what your state and local officials are saying" and follow their instructions whether or not to evacuate.

"The key is to make sure the public is following instructions to take precautions," he said.

He also said a lot of power outages can be expected in the affected areas and urged people to be prepared for the fact that it will take a long time to clear up after the storm due to its nature of slow moving and wide swath.

Only eight days ahead of Election Day, he said campaign was not top priority now and he was not worried about the impact of the storm on his re-election bid.

The incumbent is balancing between his job and the home stretch of his re-election campaign. Due to deteriorating weather conditions, Obama on Monday morning canceled a planned campaign event with former US President Bill Clinton in Florida and returned to Washington to monitor preparations for the approaching Hurricane Sandy.

The Obama campaign also canceled campaign stops Monday in Virginia and Tuesday in Green Bay, Wisconsin, so that Obama can stay in the capital to closely monitor the impact of the potentially deadly hurricane.

From Sunday through Monday noon, Obama has declared a state of emergency for Maryland, Massachusetts, New Jersey, Connecticut, Pennsylvania, Rhode Island and Delaware where Hurricane Sandy could cause severe damage, making federal aid available for local response and rescue.

The National Hurricane Center warned Monday morning Hurricane Sandy was now moving north-northwestward and accelerating and was expected to bring life-threatening storm surges, coastal hurricane winds and heavy Appalachian snow.

About 50 million people in an area stretching from the state of Virginia to Massachusetts were expected to feel the effects of Sandy, CNN reported.

US federal offices will be closed to the public Monday, with only emergency employees required to work, the US Office of Personnel Management said.

Nearly 10,000 flights have been canceled for Monday and Tuesday by airlines in anticipation of Hurricane Sandy.

As the storm approaches, the East Coast is bracing for a repeat of the "perfect storm" of 1991, which came around Halloween that year and killed dozens of people.

Sandy, which has killed 69 people in the Caribbean, will meet up with cold fronts coming out of the northwest and a high pressure system from Greenland, fueling it with enough energy to be as powerful as, or even worse than the 1991 storm.

Meteorologists have been using the term "Frankenstorm" to describe the havoc. Sandy, expected to make a landfall around Halloween, could affect hundreds of millions of people living along the East Coast.