The United States is expressing frustration at Russia's rejection of a U.S. proposal for missile defense cooperation.

On Saturday, Russian foreign minister Sergey Lavrov said the U.S. proposals "fall short." He indicated Russia would wait to negotiate with President-elect Barack Obama's administration.

U.S. State Department spokesman Robert Wood said Monday: "It seems that every time we put forward a proposal, they reject it."

American plans to install a radar spray in the Czech Republic and missile interceptors in Poland have contributed to a rapid decline in relations with Russia. The Kremlin says the United States is trying to undermine Moscow's nuclear deterrent. The United States says its plans are aimed at countering a threat from Iran.