* Russia's Lavrov criticises over-reaction

* Deploying missiles could take weeks

BRUSSELS  - NATO agreed on Tuesday to send Patriot missiles to Turkey to defend against a possible missile attack and voiced concern about reports that Damascus may be preparing to use chemical weapons.

"To the Turkish people we say: We are determined to defend you and your territory. To anyone who would want to attack Turkey we say: Don't even think about it," NATO Secretary-General Anders Fogh Rasmussen said after the 28-nation alliance foreign ministers took the decision at a meeting in Brussels.

NATO-member Turkey repeatedly has scrambled jets along the countries' joint frontier and responded in kind when shells from the Syrian conflict came down inside its borders, fuelling fears that the civil war could spread to destabilise the region.

It quickly welcomed the move. "This decision is important, as it demonstrates and re-confirms allied solidarity and unity in practical terms," Turkey's Foreign Ministry said in a statement.

Germany, the Netherlands and the United States plan to provide Patriot missile batteries, the ministers said, but they gave no details on numbers. Deployment is expected to take several weeks, given the need for approval by national parliaments and the logistics of delivering the missiles.

NATO ministers unanimously expressed "grave concern" about reports that the Syrian government may be prepared to use its chemical weapons, Rasmussen said. He warned earlier that any use of chemical weapons by Syria would prompt an immediate international response.

Turkey wants to reinforce its air defences to deal with the threat of ballistic missiles from Syria, particularly a potential chemical weapons' threat, a NATO diplomat said, speaking on condition of anonymity.

German Foreign Minister Guido Westerwelle said he expected the German parliament would approve Patriot deployment.

"I have already had several discussions with different parties and my impression is that the placement of defence missiles to protect Turkey in Turkey will get a broad parliamentary majority," he told reporters in Brussels.

NATO says the measure is purely defensive, but Russia, Syria and Iran have criticised the decision, saying it increases regional instability.

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