US President Barack Obama praised Russian officials for their cooperation in the investigation into the Boston Marathon bombings, but pointed to ongoing suspicions between the countries' officials that date back to the Cold War, dpa reported.
"The Russians have been very cooperative with us since the Boston bombing," Obama said at a White House press conference, pointing to conversations he has had with Russian President Vladimir Putin about the attacks allegedly carried out by two brothers with ties in the volatile Caucasus region.
"You know, obviously, old habits die hard. There are still suspicions sometimes between our intelligence and law enforcement agencies that date back 10, 20, 30 years, back to the Cold War," Obama said. "But they're continually improving."
Dual bombings at the Boston Marathon killed three spectators and wounded more than 250 others on April 15. The suspects, Tamerlan Tsarnaev and Dzhokhar Tsarnaev, allegedly later killed a police officer before leading law enforcement officials on a manhunt.
Tamerlan Tsarnaev, 26, was killed in a shootout with police during the chase, while the younger brother Dzhokhar Tsarnaev, 19, escaped and was captured hours later. He is now in a prison hospital and has been questioned by authorities.
Obama pointed to Russian intelligence sources that alerted US authorities to concerns about the older brother, Tamerlan Tsarnaev, and prompted the FBI to interview him. The agency concluded there were no ties to extremist activities at that time, but Obama noted an investigation into the handling of the case was ongoing.
"When an event like this happens, we want to go back and we want to review every step that was taken. We want to leave no stone unturned," he said.
"We want to see, is there in fact additional protocols and procedures that could be put in place that would further improve and enhance our ability to detect a potential attack?" he asked, adding "we won't know that until the investigation into the actual crime is fully completed, and that's still ongoing."
The FBI and other federal officials have faced criticism for not giving more critical attention to the Russian concerns. Lawmakers also have said intelligence was not shared adequately among various federal law enforcement agencies.
Obama defended the FBI and the Department of Homeland Security, but noted the challenges of defending the US against "self-radicalized individuals who are already here in the United States."
Director of National Intelligence James Clapper would determine whether any lessons could be learned from the handling of the case, Obama said.
Tamerlan Tsarnaev is believed to have spent up to six months last year in Dagestan and Chechnya, two Russian Caucasus republics suffering under a violent Islamist insurgency.
Relations between Washington and Moscow have been damaged in recent months as the US cracked down on Russian violators of human rights and Russia responded with a ban on US adoptions of Russian children.