"I'm hopeful that we can," Rasmussen said when asked whether NATO could reach agreement with the Russians.
Speaking after talks in London with British Prime Minister David Cameron, Rasmussen said agreement would "obviously" not be reached before a NATO summit in Chicago on May 20-21.
"We will continue our dialogue with Russia ... after the Chicago meeting," he told reporters.
Moscow said on Wednesday it would use computer modeling to show an international conference how the planned U.S. and NATO missile shield threatens its security.
A dispute over the system has slowed improvements in Russian-U.S. ties and is likely to remain an irritant after Vladimir Putin returns to the Kremlin next week for a six-year presidential term.
Washington says the shield, due to be completed in four phases by roughly 2020, is meant to counter a potential threat from Iran. Moscow says the system will undermine Russia's nuclear deterrent because it could also give the West the ability to shoot down Russian missiles.
The shield's first phase is to be declared up and running at the summit in Chicago.
Russia and NATO agreed in 2010 to seek ways to cooperate on missile defense but have failed to reach a deal. The Kremlin wants a legally binding guarantee the system will not be used against Russia. The United States says it cannot agree to any formal limits on missile defense.
(Reporting by Adrian Croft; Editing by Steve Addison)
Reuters
