New York Police's Deputy Commissioner John Miller said the suspect appeared "to have followed almost exactly to a 'T'" IS instructions on how to carry out such an attack.
The FBI says they have located a second Uzbek man, 32-year-old Mukhammadzoir Kadirov, who was wanted for questioning in connection with the attack.
Who is the suspect?
Sayfullo Saipov had reportedly lived in Tampa, Florida, before moving to Paterson, New Jersey.
He arrived in America from Uzbekistan in 2010 and is a legal resident of the country. Uber confirmed he had been working as a driver for them.
CBS News quotes an intelligence source as saying he was known to US authorities after his name was associated with the subjects of FBI counter-terrorism investigations in 2015.
The source says he had some contact with individuals who were considered radicalised extremists, at least one of whom was Uzbek. It is unclear whether those being investigated were in the US or overseas.
It is not known if Mr Saipov, who was not the main focus of the investigation, was interviewed at that time by the FBI.
What has been the reaction?
New York has increased the police presence at key transport hubs, and there will be additional uniformed and plain-clothes police on duty at Sunday's New York Marathon.
President Trump said he was taking steps to end the diversity lottery programme - the immigration system under which the suspect entered the country.
He also attacked the US justice system, and said he would consider sending the suspect to the US military prison at Guantanamo Bay, Cuba.