Obama administration officials have stressed they prefer prosecuting Mohammed and his four alleged co-conspirators in criminal courts, but they never definitively ruled out the option of shifting them back to military commission trials.

Opposition from New York officials and residents has forced the Obama administration to reconsider plans to put Mohammed on trial in federal court in lower Manhattan, near where the World Trade Center was destroyed in 2001.

City and state officials and many congressional Republicans argue that the high-security trial would put New Yorkers at risk of further attacks and cost taxpayers hundreds of millions of dollars.

The administration said it would take into account the security, logistical and cost concerns raised by New York City when making a final decision, and hoped to announce a new venue for the Sept. 11 trial within three weeks.

Attorney General Eric Holder announced last year that Mohammed's trial would take place in federal court in New York City. But as city officials opposed the idea because of costs, security and logistical concerns, some senators may try to stop any Guantanamo detainees from being brought to the United States for a civilian trial.

A bipartisan group of Democratic and Republican senators unveiled legislation last week aimed at cutting off funding for the criminal trials, arguing that the five co-conspirators did not deserve full constitutional rights and could use civilian trials to espouse their anti-American views.

"Obviously there are efforts on Capitol Hill through legislation to restrict either the type of, or the venue of, a trial for Khalid Sheikh Mohammed and his co-conspirators," White House spokesman Robert Gibbs told reporters.

Vice President Joe Biden defended the White House from critics of its approach to prosecuting accused terrorists, saying in interviews aired Sunday that it is not yet clear where Mohammed and the four other Sept. 11 suspects held at the US military prison at Guantanamo Bay, Cuba, will be tried.

Biden also said he believes Mohammed will be found guilty regardless of the venue, and said President Barack Obama will make the final decision about the trial.

Republicans and some Democrats argue that terrorists should be treated not as criminals but as enemy combatants and tried by military commission.

"These policies are ill-conceived and they need to stop and start over," said Sen. Lindsey Graham, R-South Carolina.

Graham said he favors closing the jail at Guantanamo Bay because its existence helps recruit terrorists to Al-Qaeda. But he said that treating terrorists as criminals to be tried in civilian courts "is a huge mistake that will come back to haunt us."