U.S. congressmen will meet security officials in Moscow this week to find out whether the FBI could have done more with Russian intelligence on the Boston bombing suspect to prevent the attack, one of the lawmakers said on Wednesday.
U.S. President Barack Obama's administration and the intelligence community face scrutiny over criticism they failed to see the danger from Tamerlan Tsarnaev and his younger brother Dzhokhar - the prime suspects in the twin bombings that killed three people and injured over 170 at the Boston Marathon.
Tamerlan Tsarnaev, 26, who was killed in a shootout with police, spent six months last year in Dagestan, a southern Russian province where Moscow is battling an Islamist insurgency.
U.S. Representative Dana Rohrabacher, a California Republican leading the fact-finding mission, said it wanted to find out whether the FBI acted strongly enough on Russian information that Tsarnaev was a potential threat.
"One of the things we want to find out is whether or not the FBI followed through on all of the information that was given to them," Rohrabacher said.
He said he and fellow congressmen Steve King, Paul Cook, Steve Cohen and William Keating were interested in how Tsarnaev's time in Dagestan may have radicalised him.
Although Washington and Moscow have vowed cooperate closely on counter-terrorism, both sides have accused each other of withholding information in the run-up to the bombing.
U.S. officials have said Russian security services asked the FBI about Tamerlan in early 2011 out of concern he had embraced radical Islam and would travel to Russia to join insurgents.
FBI agents interviewed him in Massachusetts in 2011 but said they found no serious reason for alarm. U.S. officials say Russia's FSB security services later failed to respond to the FBI's requests for more information about him.
Tsarnaev flew to Russia the following year on Jan. 12.