Another Democrat, Sen. Jack Reed from Rhode Island, said prosecuting the 9/11 terrorists in a military tribunal would play into their hands.
"All of these, particularly the sheikh, Mohammed, wants to be considered a holy warrior, a jihadist. And if we try him before military officers, that image of a soldier will be portrayed by the Islamic community. That's not the image we want. These are heinous murderers," Reed said on "Fox News Sunday."
And in a statement issued last Friday, current New York City mayor Michael Bloomberg said New York was well-equipped to handle the trials.
"I have great confidence that the NYPD, with federal authorities, will handle security expertly. The NYPD is the best police department in the world and it has experience dealing with high-profile terrorism suspects and any logistical issues that may come up during the trials," Bloomberg's statement read.
The president's senior adviser David Axelrod defended the administration's decision.
"We believe that these folks should be tried in New York City, as you say, near where their heinous acts were conducted, in full view in our court system, which we believe in," Axelrod said on CNN's "State of the Union."
"And frankly it's been a long time in coming. A lot of these cases have been delayed for many, many years. And now, the people who suffered so much in that attack will get the justice they deserve."
But Axelrod said the president was "informed" of the decision made by Attorney General Holder "in concert" with Secretary Robert Gates.
And Secretary of State Hillary Clinton declined to state her personal opinion on the decision.
"The attorney general determined, after consulting with veteran prosecutors, that this was a case that appropriately can be brought in our federal courts. Other cases will be brought in the military commissions. I'm not going to second-guess the attorney general," Clinton said.