A joint status report filed in federal court in Massachusetts indicates Tsarnaev's attorneys need more time to review physical evidence, "including nearly 2,000 items that reportedly are still being analyzed by the FBI and items kept at additional locations," CNN reported.
The defense also has made additional discovery requests.
Prosecutors estimate the trial would take 12 weeks, with a six-week sentencing phase if Tsarnaev is found guilty. They allege Tsarnaev acted in "an especially heinous, cruel and depraved manner" and lacks remorse, and they are seeking the death penalty.
The April 15, 2013, bombings -- which exploded about 13 seconds and 210 yards apart -- killed Krystle Campbell, 29, Lingzi Lu, 23, and Martin Richard, 8, and injured an estimated 264 others in the deadliest attack on U.S. soil since Sept. 11, 2001.
A Massachusetts Institute of Technology police officer was killed in a manhunt for Tsarnaev, 19 at the time, and older brother Tamerlan Tsarnaev, 26, who was killed in a police shootout.
Dzhokhar Tsarnaev -- a Chechnya native and former University of Massachusetts-Dartmouth student who became a naturalized U.S. citizen Sept. 11, 2012 -- was later caught hiding inside a boat in a Boston suburb.
A federal grand jury in June returned a 30-count indictment against Tsarnaev. The indictment included 17 charges that could carry the death penalty, the New York Times said.
Tsarnaev pleaded not guilty to all counts in July and remains in federal custody.
Seventy percent of Americans favor the death penalty for Tsarnaev, a nationwide Washington Post-ABC News poll published May 1 indicated.
A Boston Globe poll published Sept. 16 found 33 percent of people in Massachusetts supported the death penalty for Tsarnaev while 57 percent favored a life sentence without the possibility of parole.