Russia's president said NATO has a worthy role to play but he warned against further eastward expansion by the alliance before its summit in France and Germany on Friday, AP reported. President Dmitry Medvedev said a new trans-Atlantic security system he is calling for would include the alliance, not replace it. Angered by NATO expansion toward Russia's borders and what it sees as bias against Moscow in the Organization for Security and Cooperation in Europe, Russia called last year for the creation of an overarching new trans-Atlantic security treaty. Medvedev has brought up the idea repeatedly in meetings with European leaders. But the Western response has been lukewarm amid anger over Russia's war with Georgia and suspicions that Moscow's intention is to push NATO to the sidelines. President Barack Obama pleased Medvedev on Wednesday before the G-20 summit in London by agreeing to take his initiative into account in discussions on security, a more receptive approach than the one taken by Obama's predecessor George W. Bush. After the summit, Medvedev spoke to university students in London about NATO. «Before making decisions about expanding the bloc, one must think about the consequences,» he said in remarks broadcast Friday in Russia. «I said this frankly yesterday to my new comrade, U.S. President Barack Obama.» «NATO needs to think about preserving its unity and not harming relations with its neighbors,» the state-run RIA-Novosti news agency quoted him as saying.