US President Barack Obama makes a statement to reporters at the NATO summit in Lisbon Nov 19, 2010. [Photo/Agencies]

LISBON, Portugal - President Barack Obama won NATO summit agreement to build a missile shield over Europe, an ambitious commitment to protect against Iranian attack while demonstrating the alliance's continuing relevance - but at the risk of further aggravating Russia.

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While celebrating Friday's missile shield decision, Obama also made a renewed pitch for Senate ratification back in the US of a nuclear arms treaty with Russia, asserting that Europeans believe rejection of the deal would hurt their security and damage relations with the Russians.

Two key unanswered questions about the missile shield - will it work and can the Europeans afford it? - were put aside for the present in the interest of celebrating the agreement as a boost for NATO solidarity.

"It offers a role for all of our allies," Obama told reporters Friday. "It responds to the threats of our times. It shows our determination to protect our citizens from the threat of ballistic missiles." He did not mention Iran by name, acceding to the wishes of NATO member Turkey, which had threatened to block the deal if its neighbor was singled out.

Under the arrangement, a limited system of US anti-missile interceptors and radars already planned for Europe - to include interceptors in Romania and Poland and possibly a radar in Turkey - would be linked to expanded European-owned missile defenses. That would create a broad system that protects every NATO country against medium-range missile attack.

NATO plans to invite Russia to join the missile shield effort, although Moscow would not be given joint control. The gesture would mark a historic milestone for the alliance, created after World War II to defend Western Europe against the threat of an invasion by Soviet forces.

As for the US-Russia arms treaty, Obama was backed by NATO Secretary General Anders Fogh Rasmussen of Denmark, who told reporters that the treaty, called New START and signed last April by Obama and Russian President Dmitry Medvedev, would improve security not only in Europe but beyond.

"I would strongly regret if it is delayed," Fogh Rasmussen said. "A delay would be damaging for security in Europe, and I urge all parties involved to ratify it." Obama needs 67 votes in the Senate for ratification, and many Republicans have balked at even taking a vote before the new, more heavily GOP Congress convenes in January.

The allies opened their summit by agreeing on the first rewrite of NATO's basic mission - formally called its "strategic concept" - since 1999. They reaffirmed their bedrock commitment that an attack on one would be treated as an attack on all. In that context, the agreement to build a missile defense for all of Europe is meant to strengthen the alliance.

What remains in conflict, however, is the question of the future role of nuclear weapons in NATO's basic strategy. The document members agreed to Friday says NATO will retain an "appropriate mix of nuclear and conventional capabilities" to deter a potential aggressor. Germany and some other NATO members want US nuclear weapons withdrawn from Europe.

Non-government advocates of the German view were quick to criticize what they saw as a missed opportunity here for further nuclear disarmament.

"In an astonishing demonstration of weakness, NATO heads of state have failed to tackle the Cold War legacy of the deployment of US nuclear gravity bombs in Europe, threatening the credibility of NATO members' claims to be interested in non-proliferation and global disarmament," said Paul Ingram, executive director of the British American Security Information Council in London.