"The marathon will go on because New York goes on, and it's an important event for all of New Yorkers," Cuomo said at a Wednesday press conference.
More than 51,000 people are expected to run Sunday, New York Police Chief of Department Carlos Gomez said. Another 2.5 million spectators will line the city's streets to cheer them on.
But security will be enhanced, Gomez said. Police will deploy more counter-sniper and heavy weapons teams, sand trucks and blocker vehicles. The department has more than doubled the number of observation teams and added additional rooftop observation posts, he said.
"This increase will supplement the already large substantial detail of uniformed officers that you'll see along the route," Gomez said, adding there will also be plainclothes officers among the crowds.
Helicopters will patrol the race from above, and K-9 units will be on the ground, Gomez said. Traffic control agents will be on hand to keep traffic moving, too.
"It's going to be a very safe event," Gomez said.