Proposed US missile defense sites in Poland and the Czech Republic will not affect Russian security but will be designed to intercept missiles planned by Iran that would be capable of reaching Eastern Europe, a senior defense official said Thursday. Air Force Lt. Gen. Henry A. Obering, director of the US Missile Defense Agency, rejected Russian claims that the US plan would upset the security balance. Russian officials have warned of the possibility of countermeasures. Russian Defense Minister Sergei Ivanov said Wednesday that US systems being considered could not be directed against Iran because that country has no intercontinental ballistic missiles and will not have any in the future. Obering, speaking to reporters during a telephone news conference, agreed that Iran poses no long-range threat to Eastern Europe today, "but we have to stay ahead of what we think that threat is."