Marshall Billingslea, NATO's assistant secretary general for defense investment, presented a 10,000-page report detailing four years of work by NATO experts on the threat and possible defenses.
"There is a growing threat of long-range missile attack on NATO territory, and it is timely to examine ways and means of addressing that threat," Billingslea said.
The 26-nation alliance could build an effective network of sensors and interceptors to shoot down incoming missiles without over-stretching defense budgets, he told reporters.
"A missile defense system for Europe is technologically feasible," he said. "The costs of building such a system are manageable."
NATO leaders are expected to discuss the prospects of building such a defense for Europe at a November summit in Riga, Latvia.
Billingslea refused to discuss where any missile threat to NATO nations could come from, but officials from the member states have previous expressed concern about the proliferation of technologies that could allow hostile regimes in the Middle East or North Africa building extended-range missiles. The threat is especially worrisome when coupled with nuclear warheads.
The United States is already developing its own defense system against long-range missiles through the Missile Defense Agency, which has an annual budget of US$7 billion (Ђ5.5 billion) to US$8 billion (Ђ6.3 billion).
Billingslea declined to speculate on how much a European defense system might cost NATO allies, many of whom are imposing tight limits on defense spending as they struggle to control government spending. He also refused to say how soon a European network could be operational.
NATO is already working to develop a multimillion euro (dollar) defense system designed to provide battlefield protection to troops threatened with missile attack.