ZURICH: Nato chief Anders Fogh Rasmussen rejected Russian criticism of the alliance's possible deployment of Patriot missiles near Turkey's border with Syria.
Moscow has opposed the deployment of surface-to-air missiles, which Ankara has asked for, as it fears spill-over from the civil war in its neighbour.
Rasmussen, greeted by 100 anti-Nato protesters when he arrived to give a speech at University of Zurich, said Russia's criticism was "not justified".
"We have made clear from the outset we will do what it takes to defend our ally Turkey," he said in answer to a question.
He said the deployment of the missiles, which can intercept missiles or planes, will "serve as a deterrent to possible enemies even thinking of attacks and help preserve stability along our southern borders. The move will be "purely defensive".
Making the first visit to neutral Switzerland by a Nato secretary-general since 2004, he said "the Turks are increasingly worried about the situation" on the 900-km border.
Nato ambassadors have no decision but the US, Germany and the Netherlands viewed Turkey's request positively. France has also backed it.
Syria condemned Turkey's request, calling it "provocative". A ministry source told the state TV Damascus will hold Turkey's prime minister responsible for increasing tensions along the frontier.
Turkish Foreign Minister Ahmet Davutoglu blamed Syria for heightened tensions by having attacked its people with tanks and warplanes "without any regard for any rules of war". "There exists such a situation next to Turkey, that Turkey has to take measures... aimed at defence."
Syrian rebels lack advanced heavy weaponry to remove troops in main cities and remain vulnerable to frequent air strikes.