William Lynn, the deputy U.S. defense secretary, told an audience at the U.S. Missile Defense Conference in Washington that the threat from ballistic missiles was increasing, the U.S. Defense Department said.
"That threat is growing both quantitatively and qualitatively -- systems that could someday be deployed against our forces are becoming more accurate and harder to defeat, while attaining greater ranges," he said.
Lynn said Washington recognized the threat from ballistic missiles almost immediately after German forces fired V-2 missiles on Great Britain during World War II.
In the years following the world wars, he said, defense officials considered a ballistic deterrent a impossible technological feat.
But more than five decades of "concerted investment," he said, has resulted in a system in which the U.S. homeland was protected from long-term missile threats while U.S. national interests were protected from short-range missiles overseas.
"To counter the regional threat … we need to devote further resources to missile defense capabilities," Lynn said. "The safety of our deployed forces and allies depend upon this investment."