(Adds details on defense motion for change of venue)
BOSTON, Jan 22 (Reuters) - Opening statements in the trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev have been postponed as jury selection has taken longer than expected, meaning lawyers will not begin presenting cases Monday as planned, the court said on Thursday.
The delay comes as Tsarnaev's attorneys launched a fresh effort to move the trial outside of Boston, arguing that it will be impossible to find an unbiased panel of jurors in the city where the attack took place.
"It is not possible yet to specifically target a new start date," a spokeswoman for the U.S. District Court for the District of Massachusetts said in a statement.
Tsarnaev is accused of setting off twin pressure-cooker bombs at the finish line of the Boston Marathon in 2013, killing three people and injuring more than 260 in the worst such incident on U.S. soil since the Sept. 11, 2001, attacks.
He faces execution if convicted.
The challenge of selecting 12 jurors and six alternates in the high-profile trial became clear last week, as candidates expressed extreme views on Tsarnaev and the question of when to impose the death penalty.
The jury candidates have already made it through a first round of screening that began in early January, which saw more than 1,350 potential jurors fill out questionnaires.
Defense attorneys on Thursday launched their third motion for a change of trial venue, saying jurors examined so far support their theory that a fair trial is not possible in Boston. Previous requests have been denied by U.S. District Judge George O'Toole, after prosecutors argued jury selection would be a challenge anywhere in the United States.
Some 85 percent of prospective jurors screened have said they either believe Tsarnaev is guilty, or have some self-identified connection to the case, according to documents filed by Tsarnaev's defense on Thursday in support of the new change of venue motion.
"Great local prejudice will prevent a fair trial by an impartial jury in violation of Mr. Tsarnaev's constitutional rights to due process of law and a fair trial," the documents said.
Prosecutors say Tsarnnaev, 21, and his older brother Tamerlan worked together on the bombing, and that the ethnic Chechens were influenced by radical Islam. Tamerlan was killed in a shootout with police days after the bombing.
A new proposed date for the start of opening statements in the case is expected to be released next week, the court said. (Reporting by Richard Valdmanis; Editing by Jeffrey Benkoe and Bernadette Baum)