Millions of people stricken by the massive storm Sandy across the US Northeast will attempt to resume normal lives on Wednesday as companies, markets and airports reopen, despite projections of power and transit outages lasting several more days.

Sandy, which has killed at least 110 people from the Caribbean to Canada, has pushed inland and dumped snow in the Appalachian Mountains. Its remains slowed over Pennsylvania, and it was expected to move north toward western New York and Canada, the National Weather Service said.

US President Barack Obama, who faces a tight re-election battle on November 6, sent his support.

"America is with you. We are standing behind you and we are going to do everything we can to help you get back on your feet," he said.

More than 8.2 million homes and businesses remained without electricity across several states as trees toppled by strong winds tore down power lines.

According to initial industry estimates. insured losses from Sandy could run $7-15 billion (5.4-11.5 billion euros).

NYC underwater

Authorities and residents in New York City struggled to clear debris and restore power after a record storm surge of nearly 14 feet (4.2 meters) of water flooded road and rail tunnels and triggered massive fires.

In the lower half of Manhattan, a quarter million residents remained without power after a transformer explosion at a Con Edison substation Monday night.

"Restoring power and mass transit remain the two biggest challenges in the days ahead," New York City Mayor Michael Bloomberg told reporters.

"This is the end of the downside, and hopefully from here it is going up," Bloomberg said.

Buses have returned to darkened streets eerily free of traffic and the New York Stock Exchange is set to reopen its trading floor Wednesday.

Obama and Romney show support

Less than a week before Americans go to the polls, Obama planned to tour flooded areas alongside New Jersey Governor Chris Christie, a backer of the president's Republican rival, Mitt Romney.

Romney was meanwhile set to return to the campaign trail in Florida after canceling events Monday and Tuesday to focus on rescue and recovery work.

Obama strove to display leadership in the face of the storm to avoid the mistakes of his predecessor George W. Bush, whose bungled response to Hurricane Katrina in 2005 tainted his presidency.

"Do not figure out why we can't do something. I want you to figure out how we do something," he told government officials during a surprise visit Tuesday to the American Red Cross in Washington.

hc/slk (AP, AFP, Reuters)