US President Barack Obama was to return to the campaign trail Thursday after a hiatus imposed by the devastating cyclone Sandy as East Coast residents confronted the daunting task of rebuilding. With just five days left before the presidential election, Obama was to swing through vital battleground states a day after touring New Jersey\'s devastated coastline and vowing to stay with flood victims \"for the long haul.\" Millions remained without power and entire communities up and down the coast were still flooded or cut off after one of the largest storms in US history battered the northeast, killing dozens of people and flooding lower Manhattan. In New York the subway resumed limited service after the worst disaster in the system\'s 108-year history, but the Big Apple was split in half, with much of the lower Manhattan financial district still flooded and off the grid. The city said the subway would be free of charge for Thursday and Friday in a bid to reduce traffic gridlock, but three days after the storm subway lines between Manhattan and Brooklyn remained severed. The stock exchanges and John F. Kennedy and Newark Liberty airports reopened Wednesday, but more than six million homes and businesses, the majority of them in New York state and neighboring New Jersey, remained without power. US media reports said 72 Americans had been confirmed dead across 15 storm-ravaged states, bringing Sandy\'s overall toll to 144, including Canada and the Caribbean, where Haiti and Cuba were hit particularly hard. On Wednesday Obama comforted storm victims and vowed to help rebuild communities as he surveyed the damage in New Jersey, where a massive relief operation had swung into gear with tens of thousands of homes under water. Setting the heated politics of the campaign aside, Obama was accompanied by New Jersey Governor Chris Christie, a prominent Republican and supporter of White House hopeful Mitt Romney, who was also keeping the focus on the storm. Obama and Christie clambered aboard the president\'s Marine One helicopter to fly over New Jersey\'s Atlantic coast -- over houses tipped off their foundations, streets inundated with sand, and still-flooded neighborhoods. \"You guys are in my thoughts and prayers. We are going to be here for the long haul,\" Obama told a group of evacuees at a makeshift shelter. \"We are here for you. And we will not forget. We will follow up to make sure that you get all the help that you need until you\'ve rebuilt,\" he said.Although the main focus was on New Jersey and New York, particularly lower Manhattan and Long Island, Obama said he was also concerned about Connecticut and West Virginia, where heavy snows had made certain areas inaccessible. New York\'s LaGuardia airport was expected to reopen later on Thursday, with limited service. At last count, 19,500 flights had been canceled because of Sandy, tracking service flightaware.com said. Some 300,000 gallons of diesel spilled into the waters off New York City when a storage tank at a nearby New Jersey refinery ruptured, prompting a massive containment and clean-up effort, CNN reported late Wednesday. Large sections of New York, including the famed skyline of lower Manhattan, remained without electricity, and schools throughout the city were to remain shuttered for the rest of the week. Bellevue Hospital, the oldest in the country, decided to evacuate its remaining 500 patients on Wednesday after flooding inundated the basement and knocked out electricity. Meanwhile, Romney gingerly returned to the campaign trail in the key swing state of Florida on Wednesday, but he too addressed the plight of storm-battered Americans hundreds of miles to the north, asking supporters to donate to relief efforts. Obama was set to attend events planned in vital swing states Wisconsin, Nevada and Colorado on Thursday. Some 10,000 National Guard troops have deployed to storm-hit states to help local authorities rescue stranded survivors, remove debris, direct traffic and assess the damage from the air, the Pentagon said. Insured losses from Sandy could run between seven and 15 billion dollars (5.4 to 11.5 billion euros), according to initial industry estimates.