(Adds quote form U.S. Senator, New York mayor)
By Gina Cherelus and Barbara Goldberg
NEW YORK, Nov 2 (Reuters) - U.S. President Donald Trump on Thursday reiterated his call that the Uzbek immigrant accused of killing eight people by speeding a rental truck down a New York City bike path should get the death penalty.
The suspect, Sayfullo Saipov, told investigators he was inspired by watching Islamic State videos and began planning Tuesday's attack a year ago, according to a criminal complaint filed in federal court against him on Wednesday.
Saipov, 29, also said "he felt good about what he had done" and asked for permission to display the flag of the militant group Islamic State in his hospital room, the complaint said.
Trump had suggested on Wednesday sending Saipov to the Guantanamo Bay military prison in Cuba, where terrorism suspects apprehended overseas are held, but on Thursday he said doing this would have been too complicated.
"Would love to send the NYC terrorist to Guantanamo but statistically that process takes much longer than going through the Federal system...," Trump said on Twitter on Thursday. In a subsequent tweet, he added, "...There is also something appropriate about keeping him in the home of the horrible crime he committed. Should move fast. DEATH PENALTY!"
Saipov faces two charges, one of which carries the death penalty if the government chooses to seek it, acting U.S. Attorney Joon Kim said.
The charges are one count of violence and destruction of motor vehicles causing the deaths of eight people and one count of providing material support and resources to a foreign terrorist organization - Islamic State, also known as ISIS.
The maximum penalty for the first is death; the maximum for the second life in prison, Kim said.
Saipov faces the possibility of execution because he was charged under federal law; had he been charged in a state court he would not have faced this risk as New York state laws do not allow for execution.
When asked by reporters whether he thought Saipov should be executed if convicted, New York City Mayor Bill de Blasio said he categorically opposes the death penalty.
"I'm not someone who believes in the death penalty in general, I just don't," de Blasio told a press conference near the site of Saipov's attack. "I believe this is an individual who should rot in prison for the rest of his life."
Dzhokhar Tsarnaev, the surviving member of a pair of ethnic Chechen brothers who killed three people and injured more than 260 when they bombed the 2013 Boston Marathon in an attack inspired by the al Qaeda militant group, was sentenced to death in 2015. He is the only inmate among the 61 people on federal death row convicted for an act charged as terrorism.
U.S. Senator Lindsay Graham, a Republican, on Thursday criticized the Justice Department for charging Saipov in the courts, rather than treating him as an enemy combatant.
"I'm dumbfounded as to why the Trump Administration still follows the Obama playbook when it comes to dealing with terror suspects," Graham said in a statement.
Declaring Saipov an enemy combatant would have allowed investigators to interrogate him without having a lawyer present. The suspect waived his right to remain silent or have an attorney when he agreed to speak to investigators from his bed at Bellevue Hospital Center in Manhattan, where he was being treated after being shot by a police officer, according to the criminal complaint.
The complaint said he was particularly motivated by a video where Abu Bakr al-Baghdadi - the leader of Islamic State - exhorted Muslims in the United States and elsewhere to support the group's cause.
The Federal Bureau of Investigation said it had located another Uzbek man, Mukhammadzoir Kadirov, 32, wanted for questioning as a person of interest in the attack.
U.S. law enforcement officials, speaking on condition of anonymity because the investigation was continuing, told Reuters that Saipov had been in contact with Kadirov and another person of interest in the investigation.
Five Argentine tourists, a Belgian, a New Yorker and a New Jersey man were killed in Tuesday's attack. It was deadliest in New York City since the Sept. 11, 2001, attack when hijackers crashed two passenger planes into the World Trade Center, killing more than 2,600 people.
Saipov, who lived in Paterson, New Jersey, allegedly used a pickup truck rented from a New Jersey Home Depot to run down pedestrians and cyclists along a 20-block stretch of the Manhattan bike path, before slamming into a school bus.
Additional reporting by Mark Hosenball in Washington and Brendan O'Brien in Milwaukee; Writing by Scott Malone; Editing by Chizu Nomiyama and Frances Kerry