BEIRUT - NATO accused Syrian President Bashar Assad's forces of firing Scud missiles that landed near to the Turkish border, in explaining why it was sending anti-missile batteries and troops to the bloc's frontier.
The Syrian government, which finds itself under attack from rebels in the capital Damascus and by a diplomatic alliance of Arab and Western powers, denies firing such long-range, Soviet-built rockets and had no immediate comment on the latest charge.
Admiral James Stavridis, the American who is NATO's military commander, wrote in a blog on Friday: "Over the past few days, a handful of Scud missiles were launched inside Syria, directed by the regime against opposition targets. Several landed fairly close to the Turkish border, which is very worrisome."
It was not clear how close they came. NATO member Turkey, once friendly toward Assad but now among the main allies of the rebels, has complained of occasional bullets and artillery fire, some of which has been fatal, for many months. It sought the installation of missile defenses on its border some weeks ago.
"Syria is clearly a chaotic and dangerous situation; but we have an absolute obligation to defend the borders of the alliance from any threat emanating from that troubled state," Stavridis wrote.
Batteries of US-made Patriot missiles, designed to shoot down the likes of the Scuds popularly associated with Iraq's wars under Saddam Hussein in the 1990s, are about to be deployed by the US, German and Dutch armies, each of which is sending up to 400 troops to operate and protect the rocket systems.
The Syrian government has accused Western powers of backing what it portrays as a Sunni Islamist "terrorist" attack on it and says Washington and Europe have publicly voiced concerns of late that Assad's forces might resort to chemical weapons solely as a pretext for preparing a possible military intervention.
In contrast to NATO's air campaign in support of Libya's successful revolt last year against Muammar Gaddafi, Western powers have fought shy of intervention in Syria. They have cited the greater size and ethnic and religious complexity of a major Arab state at the heart of the Middle East - but have also lacked UN approval due to Russia's support for Assad.
Moscow reacted angrily on Friday to the way US officials seized on comments by a top Kremlin envoy for the Middle East as evidence that Russia was giving up on Assad. Comments by Mikhail Bogdanov on Thursday in which he conceded Assad might be ousted did not reflect a change in policy, the Foreign Ministry said.
Assad's diplomatic isolation remains acute, however, as Arab and Western powers this week recognized a new, united coalition of opposition groups as Syria's legitimate leadership. Large parts of the country are no longer under the government's control and fighting has been raging around Damascus itself.
European Union leaders who met in Brussels on Friday said all options were on the table to support the Syrian opposition, raising the possibility that non-lethal military equipment or even arms could eventually be supplied.
In their strongest statement of support for the Syrian opposition since the uprising began 20 months ago, EU leaders instructed their foreign ministers to assess all possibilities to increase the pressure on Assad.
With rebels edging into the capital, a senior NATO official said that Assad is likely to fall and the Western military alliance should make plans to protect against the threat of his chemical arsenal falling into the wrong hands.