U.S. President Barack Obama and his Russian counterpart, Vladimir Putin, say their two countries will increase security and intelligence cooperation in the wake of the Boston Marathon bombings.
The two leaders spoke by phone on April 29. The White House said Obama expressed his "appreciation" of Russia's close cooperation after the attack.
The suspected bombers had ties to Russia's volatile and mostly Muslim North Caucasus.
Suspect Dzhokhar Tsarnaev was captured after his brother Tamerlan was killed following a shoot-out with police.
U.S. officials have said Russia separately tipped off the FBI and the CIA in 2011 with concerns that Tamerlan Tsarnaev may have been a radical Islamist, raising questions about U.S. authorities' handling of the case.
Putin and Obama also vowed that the two countries would work together to ensure security at the 2014 Winter Olympics, which Russia is hosting in Sochi.
While speaking with Putin, Obama also emphasized U.S. concerns about chemical weapons in Syria.
The two leaders agreed to stay in touch on the issue and that Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov would continue discussions on Syria.
The United States is examining intelligence reports about the alleged use of chemical weapons by the Syrian government.
White House spokesman Jay Carney said the United States would weigh the evidence carefully.
"There is much more to be done to verify conclusively that the red line that [President Barack Obama] has talked about has been crossed," Carney said. "And it's very important that we take the information that has been gathered thus far and build upon it because an assessment of varying degrees of confidence is not sufficient on which to base a policy reaction."
Obama has said that, if the use of such weapons were proven, it would bring "enormous consequences" for the Syrian regime.
With reporting by AP and Reuters