"There are positive things, and topics that we disagree on. But still there hasn't been any forward progress," Dmitry Medvedev told a news conference after a summit of the Group of Eight leading nations on Japan's northern island of Hokkaido.
Medvedev and U.S. President George W. Bush met on the sidelines of the G8 summit, which is focusing on the global economy and climate change, on Monday.
Moscow has strongly opposed the possible deployment by the U.S. of interceptor missiles in Poland and a radar in the Czech Republic as a threat to its security and nuclear deterrence. Washington says the defenses are needed to deter possible strikes from "rogue states."
Russian presidential aide Sergei Prikhodko quoted Medvedev Monday as saying at his meeting with Bush that the idea of creating a missile base in post-Soviet Lithuania as an alternative to plans for Poland would be "absolutely unacceptable" to Russia.
Medvedev also said Monday that moves proposed by Washington to allay Moscow's missile shield concerns have been too vague.
Medvedev said he and Bush agreed that the election campaign in the United States should not cause any hold ups in bilateral contacts. He said Russia wants a "constructive dialogue" with any U.S. leader.
Ties between the two former Cold War foes have been strained in recent years over a host of other issues, including differences on Kosovo's independence and Iran's controversial nuclear program. There is also controversy over the Soviet-era Jackson-Vanik amendment, which restricts Russian-U.S. trade relations.
Washington has also been critical of Russia's democratic record under the current leader's predecessor Vladimir Putin, who is now the country's premier.