A group against bringing the self-professed mastermind of the September 11 attacks to trial in a US civilian court will hold a rally in New York demanding Washington reconsider its decision, the group said.

The 9/11 Never Forget Coalition said it will hold a rally on December 5 at a park adjacent to the Manhattan federal courthouse where Khalid Sheikh Mohammed and four others will be tried just blocks from Ground Zero.

No date has been announced for the suspects' transfer to New York or their first appearance in court.

Debra Burlingame, a co-founder of the group, said the trial gives Mohammed the opportunity to wage "jihad in the courtroom." The group supports trying the men before a military tribunal.

US Attorney General Eric Holder has defended his decision to move the trials from the Guantanamo Bay prison in Cuba to a federal criminal court in New York, saying the men can be tried fairly and successfully in New York.

The decision has divided the families of victims. Some say the trial is an opportunity to face the perpetrators of the September 11 attacks and help bring closure while others say the men should be treated like war criminals.

"We are giving them the biggest stage that they could possibly want," said Tim Brown, a retired New York City firefighter who said he lost dozens of friends in the attack. "We are in a pre-9/11 mentality."

Burlingame declined to estimate how many people she expected to attend the rally.