James Appathurai, a deputy assistant NATO Secretary General, said the alliance would like to reach a missile defense deal with Moscow by NATO’s summit in Chicago next May, but added that he wouldn’t “gamble on expectations.”

“We are always, of course, optimistic at NATO,” Appathurai said at a news conference.

Russia says the US-led missile defense plan could threaten its nuclear forces, undermining their deterrence potential. It has agreed to consider NATO’s proposal last fall to cooperate on the missile shield, but talks have been deadlocked over how the system should be operated. Russia has insisted that the system should be run jointly, which NATO has rejected.

Appathurai insisted that the alliance’s 28 members share a treaty obligation to provide security for each other and can’t outsource that.

Appathurai argued that the alliance has proposed to engage Russia by sharing data and coordinating a response. He also mentioned a US proposal for Moscow to have a close look at the shield’s technical capabilities and see that it won’t threaten its security.

The NATO proposals have failed to impress the Kremlin, which has continued to push for legal guarantees that the future system wouldn’t threaten Russia.

Russian President Dmitry Medvedev has warned that the failure to reach agreement on missile defense may prompt Russia to deploy new offensive weapons, triggering an arms race.

Despite the missile defense dispute, Appathurai argued that the current relations between NATO and Russia are “broader and deeper than they have ever been.” He pointed at Russia providing a vital overland supply link for NATO forces in Afghanistan and said the two sides have cooperated successfully on counter-terrorism, anti-drug and counter-piracy missions.

Appathurai and other NATO officials and military officers opened a four-day seminar Tuesday to brief their Russian counterparts on the alliance’s missions and plans.

“It’s best to understand each other’s perspective, to exchange ideas and to identify best practice,” said British Maj. Gen. Simon Porter. “The future is about working together and understanding each other.”

Russian Gen. Vladimir Yakovlev, the head of the General Staff of the Russian armed forces’ academy, said meetings like this week’s seminar will help narrow differences.