Nato leaders have approved plans to expand a European missile defence system that would protect all of the military alliance's member nations including the US.
Barack Obama, the US president, announced the agreement on Friday at the end of the first day of a summit of leaders from the 28-member grouping in Lisbon, the Portuguese capital.
The system would add security to the US's own system based in North America.
"For the first time, we've agreed to develop a missile defence capability that is strong enough to cover all Nato European territory and populations as well as the United States," Obama said.
He said that the shield "offers a role for all of our allies, it responds to the threats of our times. It shows our determination to protect our citizens from the threat of ballistic missiles".
"An attack on one Nato member is an attack on all,'' he said.
However, officials were careful not to suggest where the ballistic missile threat could come from after Nato-member Turkey raised objections to a system specifically designed to stop attacks from Iran.
"We are categorically opposed to have a country named [as a threat] and our request appears to have been accepted," Abdullah Gul, the Turkish president, told reporters before leaving Ankara, the Turkish capital, to attend the summit.
"Turkey cannot join a project that is aimed at a specific country," he said, stressing that Nato was a defensive alliance aimed at defending its members against any ballistic threat and is not an organisation designed "to intimidate and threaten".
Turkey's president Gul successfully lobbied against naming Iran as a threat [AFP]
"The project must cover all [Nato] members without exception ... It will not be aimed at Iran, we said it," he said.
Diplomats at the summit said there had been intense debate in the run-up to the summit about whether Iran should be targeted as a specific threat in the public document they adopt.
The US had asked Turkey, a Nato-member, to host some of the radar defences and to approve the proposal.
Turkey is mindful of its delicate position with neighbouring Iran and said it would refuse to sign a Nato document that names Iran as the threat in the final declaration.
"Turkey does not want to be the military front for Nato, it wants to be the diplomatic face of Nato in the Arab and Muslim world," Marwan Bishara, Al Jazeera's senior political analyst, said.
"But any state that would dare launch a missile against Europe would be obliterated the day after - so who would be so suicidal as to launch a missile against Europe?"
Anita McNaught, Al Jazeera's correspondent in Istanbul, said: "The compromise that Nato seems to have arrived at, even ahead of this meeting, is that no countries will be cited and the stress will be on this being a defensive system and not an offensive one.
"[Turkey has] worked extremely hard in this region to deal with the perception of threat among its neighbours, to de-escalate the sense of jeopardy and danger and defensiveness and offensiveness ... that has caused so many problems."
McNaught said that Turkey also wanted to make sure that the system would in no way be used to protect Israel from attack.
"It [Turkey] wants to be clear that this system is for the defence of territories from Turkey's eastern border, westward. It wants to be sure this is not a 'proxy' defence system for Israel." she said.
"It does not want any of the intelligence gathered through this system to be shared with Israel."
Anders Fogh Rasmussen, Nato's secretary general, said that there was an urgent need for the new missile defence system.
"The fact is that more than 30 countries in the world have or are acquiring missile technologies, some of them can even hit targets in the Euro-Atlantic area. And we intend to build a missile defence system to defend against any of these threats."
The expanded system is expected to cost $273 million over the next 10 years, Rasmussen said.
Dmitry Medvedev, the Russian president, who will attend the summit on Saturday has previously fought against the missile shield, saying it was a threat to his country's own nuclear deterrence.
But Nato on Friday decided to invite Russia to join the defence shield, extending its protection across Russian territory.
Source: Al Jazeera and agencies