Russian Defense Minister Anatoly Serdyukov and his U.S. counterpart Leon Panetta have discussed issues of international security and the proposed European missile defense shield. Serdyukov also invited Panetta to pay an official visit to Moscow during the telephone conversation, a Russian Defense Ministry statement said. Russia and NATO agreed to cooperate on the so-called European missile defense system at the Lisbon summit in November 2010. NATO insists there should be two independent systems that exchange information, while Russia favors a joint system with full-scale interoperability. Russia also demands legally binding guarantees that NATO missile defense systems will not be directed against it.