Strolling side-by-side, U.S. President Barack Obama and one of his fiercest Republican foes, Gov. Chris Christie of New Jersey, toured destruction zones in the storm-ravaged state, pledging that no victims of Sandy would be overlooked.

"We don't leave anybody behind," the president told a New Jersey crowd Wednesday, during a stop in one of four U.S. East Coast states that bore the brunt of post-tropical storm Sandy.

Other states the president noted as in dire need of assistance after the superstorm, which killed dozens, included New York, Connecticut and West Virginia, where heavy snow from a Sandy-related blizzard buried roads and was blamed for at least five deaths.

The president said the focus of relief efforts would be on those four regions for the time being, and added that he did not want Americans to become disillusioned because the mess will not be cleaned up overnight.

"We will not forget. We will follow up to make sure that you get all the help that you need until you rebuild," he said, adding "we will not quit until this is done."

Obama also said he has instituted a 15-minute rule for his team. Staff must return all phone calls within 15 minutes to ensure rescue efforts are efficient.

"We are not going to tolerate red tape," Obama said. "We are not going to tolerate bureaucracy."

Earlier in the day, the president and Christie spoke with locals in the worst-affected areas in the state.

The New Jersey governor said Wednesday that Halloween would be postponed for five days in order to direct all available resources toward disaster recovery. He signed an executive order rescheduling celebrations for Monday.

Christie also gave the president rare praise, saying he was pleased with Obama's response to the disaster. He said he mentioned some resources needed and Obama "sprung into action immediately to help get us those things while we were in the car riding together."

New York Stock Exchange reopened

Millions of people in the northeastern U.S. corridor pummelled by Sandy are continuing to work towards regaining some normalcy as airports reopen, vehicles return to the streets and stock exchanges resume trade following a two-day closure.

A man carries his wife through the floodwaters to a National Guard truck in Hoboken, N.J. (Gary Hershorn/Reuters)

New York Mayor Michael Bloomberg stood on the storied trading floor of the New York Stock Exchange on Wednesday morning and rang the opening bell — a symbolic gesture as the region struggles to recover after the lashing winds and storm surge killed as many as 72 people. The stock exchange was to run on generator power, though some 650,000 in the city were still in the dark.

New York's three major airports were expected to be open Thursday morning with limited flights. Limited service on the subway, which suffered the worst damage in its 108-year history, would resume Thursday.

The massive storm system destroyed homes and businesses, causing billions of dollars worth of damage, and left millions without power, before moving across Pennsylvania on a predicted path toward upstate New York and Canada.

'It's good for the city, good for the country, it's good for everyone to get back to work.'—New York City Mayor Michael Bloomberg

Rescuers in several states combed through neighbourhoods gutted by flooding, strewn with debris and devastated by fire.

In New York, 500 patients were evacuated from Bellevue hospital, CBC's Melissa Kent reported from Manhattan. The hospital was running on backup generators, she said, but it was unclear if they failed and forced the evacuation.

City schools and parks remained closed, and rescuers continued to search devastated neighbourhoods.

However, rush-hour traffic in New York City began to thicken again as people started returning to work. New York City buses were also back on city streets with partial service, but at no cost to board.

At the stock exchange, running on generator power, Bloomberg gave a thumbs-up and rang the opening bell to whoops from traders on the floor.

"It's good for the city, good for the country, it's good for everyone to get back to work," the mayor told CNBC moments later while leaving the exchange building on Wall Street.

Subways remained closed, but Gov. Andrew Cuomo said partial service would resume on Thursday when 14 of the 23 lines may be operational. Inspectors will run tests overnight, he said.

"[Subways are] really the lifeline of the city, 8.5 million people use the transit system every day in New York," Kent reported.

"It's the largest in North America. But several of the tunnels were flooded during the storm … it might even be a week before the entire subway is back up and running."

Much of the initial recovery efforts focused on New York City, the region's economic heart. Bloomberg said it could take four or five days before the subway, which suffered the worst damage in its 108-year history, is running at full speed again.

Kennedy and Newark Liberty airports have reopened with limited service. LaGuardia Airport, which suffered far worse damage and where water covered parts of runways, remained closed.

At the height of the disaster, 8.5 million households lost electricity — some as far away as Michigan. Nearly a quarter of those without power were in New York, where Lower Manhattan's usually bright lights remained dark for a second night.

On Wednesday, more than six million homes and businesses were still without power, including four million in New York and New Jersey. Electricity was out as far west as Wisconsin and as far south as the Carolinas.

New Jersey postpones Halloween

The scale of the recovery challenge was clear across the Hudson River in New Jersey, where National Guard troops arrived in the heavily flooded city of Hoboken to help evacuate about 20,000 people still stuck in their homes and deliver ready-to-eat meals. Live wires dangled in floodwaters that Mayor Dawn Zimmer said were rapidly mixing with sewage.

The city appealed for additional aid, including boats and generators. Zimmer asked local businesses to get water and non-perishable goods to city hall.

Traders and staff report to work at the New York Stock Exchange on Wednesday. Mayor Michael Bloomberg rang the opening bell at the storied trading floor on Wednesday after it was closed for two days because of superstorm Sandy. (Brendan McDermid/Reuters)

"We are doing what we can but we really need more help," said her spokesman, Juan Melli.

And new problems arose when firefighters were unable to reach blazes rekindled by natural gas leaks in the heavily hit shore town of Mantoloking.

"I’ve taken this action to minimize additional risks to lives and the public safety as we begin the process of rebuilding and recovering from Hurricane Sandy,” said Christie in a statement.

“In too many communities in our state, the damage and losses from this storm are still being sorted out, and dangerous conditions abound even as our emergency management and response officials continue their work."

Transit damage worst in 108 years

All 10 of the subway tunnels that carry commuters under the East River were flooded. But high water prevented inspectors from immediately assessing damage to key equipment, raising the possibility that the nation's largest city could endure an extended shutdown of the transit system.

The chairman of the state agency that runs the subway, Joseph Lhota, said service might have to resume piecemeal, and experts said the cost of the repairs could be staggering.

Power company Consolidated Edison said it would be four days before the last of the 337,000 customers in Manhattan and Brooklyn who lost power have electricity again, and it could take a week to restore outages in the Bronx, Queens, Staten Island and Westchester County. Floodwater led to explosions that disabled a power substation Monday night, contributing to the outages.

With files from The Associated Press