Vershbow told the Royal United Services Institute's missile defense conference in London the NATO alliance took its missile defense obligations seriously.
"Missile threats to our alliance territory and populations are real and growing," he said during a speech Wednesday evening.
U.S. considerations for an Eastern European missile defense shield frustrated the Russian government, which said Western missiles would upset the strategic balance of power.
Vershbow said he doubted Russia's concern were legitimate, but said cooperation may allay some of the anxiety.
"The idea is for NATO and Russian officers to work together, on a full-time basis, to develop plans for intercepting missiles that may be launched against either party in a range of scenarios," he said.
Allied security concerns escalated in February when North Korea conducted an underground nuclear test, its third. A series of war games in the region culminated with a decision by North Korea to test fire missiles offshore though the threat has since diminished.