The alleged attacker, Sayfullo Saipov, told FBI interrogators that he was inspired by the terrorist group, and Trump tweets that the group claimed him as “their soldier.”
Trump says, “Based on that, the Military has hit ISIS “much harder” over the last two days. They will pay a big price for every attack on us!”
It is not immediately clear whether Trump approved any direct retaliatory strikes following the attack.
The president is calling Saipov a “degenerate animal.”
Daesh has claimed responsibility, without providing proof, for a truck attack earlier this week that killed eight people in the deadliest assault on New York City since Sept. 11, 2001.
The militant group on Thursday described accused attacker Sayfullo Saipov, 29, as “one of the caliphate soldiers” in a weekly issue of its Al-Naba newspaper.
The Uzbek immigrant was charged in federal court on Wednesday with acting in support of Daesh by plowing a rented pickup truck down a popular riverside bike trail, crushing pedestrians and cyclists and injuring a dozen people in addition to those killed.
Saipov told investigators he was inspired by watching Daesh propaganda videos on his cellphone, felt good about what he had done, and asked for permission to display the group’s flag in his room at Bellevue Hospital.
Saipov was taken to Bellevue after being shot in the abdomen by a police officer before his arrest.
Earlier this week, Trump suggested sending Saipov to the Guantanamo Bay military prison in Cuba, where terrorism suspects apprehended overseas are incarcerated. But on Thursday, he said doing so would be too complicated.
The US president has also urged Congress to end the Diversity Immigrant Visa program under which Saipov entered the US in 2010.
The diversity program, signed into law in 1990 by Republican President George H.W. Bush, was designed to provide more permanent resident visas to people from countries with low US immigration rates.
Five Argentine tourists, a Belgian woman, a New Yorker and a New Jersey man were killed in Tuesday afternoon’s attack.
One of the two criminal counts Saipov faces, violence and destruction of motor vehicles causing the deaths of eight people, carries the death penalty if the government chooses to seek it, prosecutors said.
Saipov waived his right to remain silent or have an attorney present when he agreed to speak to investigators from his hospital bed, the criminal complaint said.
The Federal Bureau of Investigation (FBI) has said it has located another Uzbek man, Mukhammadzoir Kadirov, 32, who it said was wanted for questioning as a person of interest in the attack.
Citing an unnamed law enforcement official, ABC News reported on Friday that Saipov placed a telephone call to Kadirov immediately before he carried out the attack. ABC News said the significance of the call was not known.