An Afghan-born Colorado resident may have plotted an attack on New York commuter trains for this month's 9/11 anniversary, a US prosecutor has said, BBC reported.
The suspect, Najibullah Zazi, is accused of receiving explosives training in Pakistan and buying large quantities of bomb-making chemicals.
A judge has ordered that he be moved to New York to face charges of conspiracy to use weapons of mass destruction.
Since his arrest, Mr Zazi has publicly denied being a terrorist.
Mr Zazi, 24, has been ordered to be held without bail pending his transfer from Denver to New York.
Prosecutor Tim Neff told the Denver judge who approved the transfer that Mr Zazi "was in the throes of making a bomb and attempting to perfect his formulation".
"The evidence suggests a chilling, disturbing sequence of events showing the defendant was intent on making a bomb and being in New York on 9/11, for purposes of perhaps using such items," he was quoted as saying by the Associated Press news agency.
Nail polish remover
Mr Neff said the suspect had driven to New York on 9 September before suddenly returning to Denver.
Prosecutors say he returned after learning that he was being watched by federal agents.
According to an indictment by the New York federal grand jury, Mr Zazi brought "unusually large" quantities of hydrogen peroxide and nail polish remover from beauty shops to make bombs, possibly for detonation on New York commuter trains.
A government motion seeking to deny Mr Zazi bail said he had travelled to Pakistan in August 2008 where he received explosives training, AP reported.
On his return early this year he used a computer to research homemade bomb ingredients, the motion said.
Mr Zazi and his father, Mohammed, were arrested last Saturday in Denver on charges of lying to FBI agents investigating the case.
A third man, 37-year-old imam Ahmad Wais Afzali, was arrested in Queens, New York.
All three have denied any involvement in the alleged plot.
Mohammed Zazi has been ordered to be freed under court supervision, while Mr Afzali has been released on bail.