U.S. President George W. Bush began a farewell call in Russia on Saturday as the White House abandoned hope of a major agreement on missile defense during weekend talks with Russian President Vladimir Putin.

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Putin vigorously opposes U.S. plans to deploy a missile defense system in Europe, an issue that has been a major irritant in U.S.-Russia relations.

White House spokeswoman Dana Perino said it will take more than a weekend of talks to reach a consensus.

"We're going to have to do more work after Sochi," Perino told reporters traveling with Bush on Air Force One from Zagreb, Croatia, where earlier in the day the president celebrated the expansion of NATO into former communist territory.

"No one has said that everything would be finalized and everyone would be satisfied with all the preparations because we haven't even started to work on the technical aspects of the system," Perino said. "We're still in the early part of these discussions."

But, Perino added, "the dialogue is headed in the right direction and ... this meeting will be able to push that along even further."

Though Russia opposes placement of a missile defense system in its backyard, the concept won the full support of NATO leaders at a summit earlier this week in Bucharest, Romania, which Bush attended.

Perino said U.S. officials are working to convince Russia that it has little to fear from such a system.

"I think we have made great strides in bringing confidence to the Russians that this system is not aimed at Russia and Russia is not the enemy," she said. "You've heard the president say the Cold War is over, and if you look at what NATO just did this past week on missile defense, people have come to the realization that together, working cooperatively, we can help deter or prevent an attack from a rogue nation in the Middle East, not from Russia."

Aside from the NATO endorsement, the anti-missile program also advanced with the Czech Republic's agreement to accept a radar system that would track the sky for any threats. The White House has to complete a deal with Poland where 10 interceptor rockets would be based.

The setting sun cast a bright glare on the water as Bush's motorcade traveled a bumpy coastal highway for the 35-minute drive to Putin's retreat on the Black Sea. The Russian president greeted his American counterpart with a handshake at the door of his summer home in a heavily wooded compound.

Both leaders then went upstairs for a briefing on Sochi's preparations as host city for the 2014 Winter Olympics. They inspected a mock-up of the athletic site and a building spread across a 20-foot-long tabletop display.

"This is your yacht," Putin joked to Bush, pointing to a 3-inch white ship on an area representing the Black Sea. Bush laughed.

Their meetings, over dinner Saturday and additional talks on Sunday, will give both leaders a chance to "have a broad range of discussions on many of the issues that they've been working on over the past eight years," Perino said. She cited such areas as security cooperation, nuclear nonproliferation, counterterrorism and economic issues.

They hope to "deepen and broaden the relationship before handing it off to the next presidents," she said.

Bush and Putin, who leaves office May 7, also were expected to sign a "strategic framework" agreement that would guide the bilateral relationship into the future. Putin's hand-picked replacement, Dmitry Medvedev, will participate in some of the discussions.

"We believe we are heading toward that direction to be able to sign something. I think it will be broad," Perino said.

Bush, whose term ends in January, and Putin planned to have dinner Saturday, followed by additional talks Sunday before Bush departs for Washington.

In Croatia, Bush highlighted a separate set of differences with Putin: NATO's expansion into former communist territory. Croatia and Albania won invitations during the NATO summit to join the military alliance, while Macedonia did not, due to Greek objections.

In an outdoor speech, Bush said the invitations were "a vote of confidence that you will continue to make necessary reforms and become strong contributors to our great alliance." He reinforced the message immediately afterward by honoring NATO's newest members at lunch.

"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 the thousands packed into Zagreb's St. Mark's Square.

Such praise for the spread of democracy and the promise of Western military protection for that freedom — was unlikely to be cheered in Moscow. Bush's focus on freedom comes as his administration continues to harshly criticize increasing Kremlin authoritarianism.

Besides missile defense, Bush's drive for NATO membership for Ukraine and Georgia also roils Russia, which claimed victory when the ex-Soviet republics' aspirations to join the alliance were snubbed at the summit. But Bush and his aides have pointed out that NATO leaders pledged to eventually open the path to joining for the two countries, possibly as early as December.

Bush did not mention Ukraine and Georgia in his speech while advocating further NATO enlargement. He did mention them, however, in his weekly radio address, which is broadcast in the U.S. He commended the thousands of people in both countries who in recent years have peacefully demanded "their God-given liberty."

"The people of Ukraine and Georgia are an inspiration to the world and I was pleased that this week NATO declared that Ukraine and Georgia will become members of NATO," Bush said in the broadcast.

In Croatia, Bush also noted the success of U.S.-supported democratization in the Balkans, where the effects of the disintegration of the former Yugoslavia still affect ties between Washington and Moscow. Most recently, the United States and many of its European allies rallied around independence for the Serbian province of Kosovo. Russia, supporting Serbia, strongly opposed that.