Bush will travel April 6 to the Russian resort Sochi at Putin's invitation, following a weeklong trip in Eastern Europe highlighted by the NATO meeting, The Washington Times said.

Russia seemed to more willing to consider the proposed radar and missile base after U.S. Secretary of State Condoleezza Rice and Defense Secretary Robert Gates developed a proposal addressing Moscow's security concerns during their recent trip to Russia.

"Hopefully, we could advance our dialogue so that at some point in time we could reach agreement on this important matter (of the missile defense system)," Bush told the foreign media. "I'm optimistic we can reach accord on very important matters."

National security adviser Stephen J. Hadley said Bush will seek "to find a way in concrete terms to reassure Russia that the radar and missile installation" are designed to head off threats from the Middle East "and are not aimed at Russia."

In May, Putin will hand over the presidency to President-elect Dmitry Medvedev and will become Russia's prime minister.