The megastorm killed at least 70 people in the United States, including 24 in New York City alone, The New York Times reported, after leaving a like number dead in the Caribbean. Property damage could be as high as $20 billion throughout the Northeast, catastrophe-risk modeling firm EQECAT said.
Speaking in Brigantine, N.J., after a tour of damage caused by the massive storm, Obama said: "We are here for you and we will not forget. We will follow up to make sure that you get all the help you need until you rebuild."
Christie thanked Obama for his "personal concern" for New Jersey and said, "We will get up and we will get this thing rebuilt."
Christie said New Jersey's "challenge now is to get back to normalcy," and he once again expressed gratitude to Obama for the administration's response to the disaster.
"I'm pleased to report that he has sprung into action immediately ... while we were riding in the car together," Christie said of the president.
Obama's tour of the Garden State came as the storm headed toward Canada.
At least 6.2 million customers were without power Wednesday -- down from an estimated 8 million late Tuesday -- and more than 18,000 flights had been canceled since Sandy first started moving along the East Coast, after causing at least 67 deaths in the Caribbean.
Repair crews were reporting progress Wednesday in restoring electrical service to hundreds of thousands in West Virginia, but Kanawha County Manager Jennifer Sayre said in a release it might take until Sunday to get all service restored, The Charleston (W.Va.) Gazette reported.
By Wednesday morning, the number of Appalachian Power customers without service was about 118,000 -- down from almost 126,000 Tuesday night, the power company said.
In the northern part of West Virginia, First Energy said 100,725 of its customers were without electricity Wednesday morning, down from almost 110,000 Tuesday night -- but more service disruptions were reported later Wednesday because of new snow accumulations.
First Energy said power would not be fully restored until next week.
Dominion Virginia Power said Wednesday it has restored service to more than 90 percent of its 205,000 Northern Virginia customers affected by the storm, and -- with a few exceptions -- full restoration is expected by Thursday night.
During a conference call with reporters Wednesday, U.S. Homeland Security Secretary Janet Napolitano said the federal response to the disaster is intended to "get resources where they are needed as fast as possible without delays."
"We're asking everyone to be patient as we work with all speed we can to ... restore the necessities of life to areas affected by this storm," she said.
Red Cross Senior Vice President of Disaster Services Charley Shimanski said the organization's needs come down to two main items: blood and money. He said the storm has caused cancellation of large numbers of blood drives, putting a great strain on supplies, and he noted that providing shelter, food and other services in storm-damaged areas is very expensive.
In New York City, the state Metropolitan Transportation Authority restarted limited suburban commuter-rail service Wednesday and will resume limited subway service Thursday, New York Gov. Andrew Cuomo said.
Significant sections of the largest U.S. mass-transit system remained disabled.
Commuter-rail service was available on the Metro-North Commuter Railroad to the northern suburbs in New York and Connecticut and the Long Island Rail Road, between Manhattan and the length of Long Island. Limited subway service was to be restored between Manhattan and Brooklyn, Cuomo said.
Newark Liberty International and Kennedy International airports resumed operations, but many airlines still operated on a limited basis, said the Port Authority of New York and New Jersey, which operates the New York-area airports. LaGuardia Airport remained closed after suffering damage.
Stewart International Airport, 55 miles north of the city, also was open with limited service, the Port Authority said.
Philadelphia International Airport officials said operations were resuming Wednesday.
Amtrak said Wednesday it will provide modified Northeast Regional service beginning Thursday between Boston and New Haven, Conn., and between Newark, N.J., and points south. Amtrak said it will also operate shuttle service trains between Springfield, Mass., and New Haven, Keystone Service trains between Harrisburg, Pa., and Philadelphia, and Downeaster service trains between Boston and Portland, Maine, along with additional overnight services to and from the Northeast.
The announcement said Amtrak plans to restore modified service into and out of New York City Friday.
But no Northeast Regional service is planned between Newark and New Haven and no Acela Express service will be available for the length of the Northeast Corridor Thursday.
A huge fire burned on Mantoloking Island off the New Jersey shore, where flames could be seen shooting directly out of the sand, WABC-TV, New York, reported.
New Jersey authorities believe a gas main explosion may be the cause of the fire that spread quickly across the island, destroying several homes, the report said.
Firefighters could not reach the blaze due to storm damage on the roads leading to the island.
Neighborhoods in New Jersey were still deluged with water as Obama surveyed damage by helicopter and met with victims of the storm with Christie.
Obama, Christie and Federal Emergency Management Agency Administrator Craig Fugate took an aerial tour aboard the presidential helicopter Marine One of New Jersey areas damaged by the storm and then went to Brigantine, an island northeast of Atlantic City -- where the president told residents gathered at a community center Christie "is working overtime to make sure that as soon as possible everybody can get back to normal."
Christie told the audience it is "really important to have the president of the United States acknowledge all the suffering that's going on here in New Jersey and I appreciate it very much. We're going to work together to make sure we get ourselves through this crisis and get everything back to normal. Thank you for coming, sir."
Christie -- the keynote speaker at this year's Republican National Convention and a harsh critic of the president at times -- is drawing some criticism from conservatives and other fellow Republicans for his effusive praise of Obama's handling of the storm response.
NBC News reported Christie said he would ask Obama to direct the Army Corps of Engineers to look into rebuilding beaches to protect towns, but he said "it won't be the same because some of the iconic things are washed into the ocean."
Much of the famed Boardwalk in Atlantic City was destroyed and the resort city for gambling and conventions was all but submerged.
The U.S. Navy Wednesday sent three helicopter carrier ships -- the USS Wasp, USS Carter Hall and USS Mesa Verde -- to the New Jersey and New York coasts, NBC reported. The ships are to function as landing platforms for military and civilian agency helicopters if needed, officials said.
The National Weather Service's Hydrometeorological Prediction Center said in its 11 a.m. EDT advisory winds, rain and snowfall were diminishing, and gale warnings were in effect for portions of the Great Lakes. Winds were expected to diminish, but coastal flooding along portions of the Great Lakes was possible, forecasters said.
Rather than identifying a location for the center of the storm, forecasters said multiple centers of circulation associated with the storm were across the lower Great Lakes.
Flood watches and warnings were posted across New England and flood warnings were in effect for portions of the northern mid-Atlantic region.
Winter storm warnings and winter weather advisories were in effect along the central Appalachians, and the mountains of West Virginia into western Maryland and southwest Pennsylvania were likely to get another 2 to 4 inches of snow. West Virginia has already had 3 feet of snow and at least 2 feet of snow has fallen in parts of Maryland, Virginia and North Carolina.
New York City's Bellevue Hospital Center was evacuating 500 patients Wednesday because of problems keeping the building powered.
NewYork-Presbyterian Hospital said Wednesday it has resumed performing surgical procedures and its emergency departments and dialysis centers are fully operational.
The hospital said it is still receiving patients from other area hospitals.
Obama signed federal emergency declarations for 10 states and the District of Columbia and spoke with 20 governors and mayors on a conference call.
New York financial markets resumed trading Wednesday even though much of the city was without electricity.
At least 80 homes caught fire and burned in a Queens neighborhood.
New York's subway system suffered the most devastating damage from floodwaters in the system's 108-year history, Metropolitan Transportation Authority Chairman Joseph Lhota said Tuesday. The New York Harbor saltwater that gushed into subway tunnels may have corroded signal and switching systems, he said.
He said service would not be fully restored for at least four or five days.
New York buses began running again Tuesday afternoon and Mayor Michael Bloomberg ordered a ride-sharing program for taxis.
New York, New Jersey and Connecticut reopened many closed roads and bridges.
New York police executed several daring air rescues, dropping lifelines to rescue at least six people, including a child, the Times reported.
Police said there haven't been any signs of looting or other indications of crimes of opportunity taking place because of the storm, the Times said.
During an evening news conference Tuesday, Bloomberg said more police would be part of overnight shifts in the parts of the city still in darkness.
"This is the calm after the storm," one police officer told the Times.
Dangerous surf conditions were expected from Florida to New England for the next couple of days.