ZAGREB, Croatia — President Bush celebrated NATO's expansion into former communist territory on Saturday and urged further enlargement, highlighting differences with Moscow hours before final talks with outgoing Russian President Vladimir Putin.

Bush congratulated the Eastern European nations of Croatia and Albania for the invitations to join NATO that they won this week at the military alliance's summit in Bucharest, Romania. He urged a similar welcome for Macedonia, which snagged on Greek objections. The president reinforced that message immediately after his speech in a public square here by honoring the newest members of NATO's club over lunch.

Bush called the invitation to join NATO "a vote of confidence that you will continue to make necessary reforms and become strong contributors to our great alliance."

"Henceforth, should any danger threaten your people, America and the NATO alliance will stand with you and no one will be able to take your freedom away," he said to cheers from an audience of thousands packed into St. Mark's Square, used as the site of the inauguration of every Croatian leader for the past 700 years and considered "the center of Croatian politics."

Such praise for the spread of democracy on Russia's doorstep — and for the promise of Western military protection for that freedom — was not likely to be cheered in Moscow, however. Bush's focus on freedom comes as his administration continues to harshly criticize increasing Kremlin authoritarianism.

So, even as Bush has sought in recent days to downplay tensions between the United States and Russia, he used his overnight stay in Croatia, as well as one in the former Soviet republic of Ukraine earlier in his weeklong trip, to showcase some of the differences that have caused those tensions.

By evening Saturday, Bush was to be at Putin's summer home at the Black Sea resort of Sochi. The two are to cap an often contentious seven-year relationship that will come to end when Putin leaves office next month. They hope to produce a new "strategic framework" to guide relations to a less rocky future beyond their time in office.

Over dinner and again in talks Sunday, Bush and Putin are expected to make nice and emphasize the positive, such as the strategic framework and Russia's agreement this week to allow shipment of nonmilitary NATO supplies to Afghanistan through its territory.

But the U.S. plan to deploy a missile shield in Europe is a major source of friction between the two countries. Though the concept is vehemently opposed by Russia, it won NATO leaders' full support this week.

And the U.S. desire to see NATO open the admission process for Ukraine and Georgia also roils Russian officials.