In a political setback for President Barack Obama, the United States said today it would try self-professed September 11 mastermind Khalid Sheikh Mohammed and four others at Guantanamo Bay ("Gitmo") and not in New York City, as Obama had hoped.

The group of co-conspirators will face a military commission, rather than a US civil court.

US Attorney General Eric Holder told a news conference the decision was necessary because Congress had imposed "unwise and unwarranted restrictions" that blocked the administration from bringing any Guantanamo detainees to trial in the United States, Reuters reported.

His announcement was an embarrassing reversal of the administration's decision in November 2009 to try Mohammed in a court near the site of the World Trade Center attack that killed nearly 3,000 people.

The decision was an admission that Obama has not been able to overcome political opposition to his efforts to close the prison for terrorism suspects and enemy combatants at Guantanamo Bay and try those accused of crimes in US civilian courts, Reuters reported.