"There are tens of thousands of people who come from around the world here to run," Bloomberg said. "We’ve decided that the marathon will go on. We suspect by Sunday most of the power will be back, if not all of it.
"The bottom line is, some people said you shouldn’t run the marathon. There are an awful lot of small businesses that depend on these people. We have to have an economy."
While Bloomberg confirmed that it would take place, Thursday's NBA opener between the Brooklyn Nets and New York Knicks was postponed.
The race draws some of the world's elite distance athletes. In 2011, more than 47,000 runners finished the race, according to the event's website.
The 2009 winner Meb Keflezighi said he supports the Mayor's decision.
"It will be something positive," American Keflezighi said in a media conference call. "The city has a lot of flooding, and to see people run through it is the complete opposite. We’ll give them a good show."
His compatriot Amy Hastings, who came second in last year's LA Marathon, said she drove from Providence Rhode Island to take part in the race.
"This is going to be a great event," Hastings, 28, said. "The storm was an incredible force of nature, and if any city can pick up from it and keep going, it’s New York."