Dzhokhar Tsarnaev faces being executed if he is found guilty of the Boston Marathon bombing after defence lawyers failed to strike a plea deal with the US Justice Department.
Talks between Tsarnaev's team and prosecutors had been ongoing over a potential guilty plea to avoid a death sentence.
But discussions have stalled with the Justice Department unwilling to budge over a possible maximum punishment.
Tsarnaev's lawyer Judy Clarke previously negotiated successful plea deals for criminals including 9/11 terrorist Zacarias Moussaoui, "Unabomber" Ted Kaczysnki, and Jared Loughner, who fatally shot six and injured former Congresswoman Gabrielle Giffords.
The impasse comes as the district judge George A. O'Toole Jr. summoned 3,000 people for the start of the trial as he looks to select a jury that is "death-qualified".
Tsarnaev, 21, is charged with 30 criminal counts in the April 2013 bombings, which killed three people and injured 260 others, and for in the murder of police officer, Sean Collier, a few days after the bomb attack.
His representatives failed to secure a delay to the trial after calling for the trial to be moved away from Boston, where emotion remains high over the bombing.