Keating, D-Mass., said Thursday the Russian intelligence service FSB provided the information, including details that Tsarnaev planned to join an Islamic insurgency in Dagestan, The Boston Globe reported.
Tsarnaev, 26, and his brother, Dzhokhar, 19, are accused of detonating two bombs April 15 near the finish line of the Boston Marathon, killing three people and injuring at least 264 others.
Dzhokhar Tsarnaev is in police custody and charged with using weapons of mass destruction. Tamerlan Tsarnaev was killed April 19 in a shootout with police.
Keating's comments came during a trip to Moscow to discuss counter-terrorism cooperation in advance of the Sochi Winter Olympics next year, The Moscow Times reported.
"We understand that the Olympic Games will be a target for terrorism. What can the international community and the United States do to help you?" Keating asked Russian officials.
Boston schools pull out free condoms over wrapping complaints
Kim Kardashian, Kanye West reportedly set wedding date