If the US goes ahead with plans to build a National Missile Defense system, this will require upgrading the warning radars at Thule AFB, Greenland. But Greenland is owned by Denmark, and the Danes have declared that they will veto the expansion of the base and its radars unless the 1972 ABM Treaty is respected, which means only if the Russians agree to changes in the treaty that allow the NMD system to be built. If the US unilaterally abrogates the ABM Treaty, as many Congressional Republicans want, Denmark says it will never accept upgrading Thule AFB into a missile defense warning post as this would make Greenland a target for attack.--Stephen V Cole