"Apparently he [Rasmussen] wants to explain [NATO's] position on this issue," Lavrov told a news conference after talks in Moscow with Bangladesh's foreign minister, Dipu Moni.
"The main concern is the more weapons there are, the greater the risk that they will be used."
He said Russia, which is not a member of NATO and cannot block a decision, understood that no one intended to drag the alliance into the Syrian crisis.
"But ... in the military field, what is important is not intentions, but potential. And when potential increases, the risks grow," he said.
The West has criticized Russia, as well as China, for vetoing three UN Security Council resolutions aimed at putting pressure on Assad to end a conflict activists say has killed more than 38,000 people since protests began in March 2011.
Russia denies trying to prop up Assad, whose nation has been an avid buyer of its weapons and hosts a naval supply facility that is Moscow's only military base outside the ex-Soviet Union.
Russia understands Turkey's security concerns along its Syria border, Lavrov said. “However, we want to warn against provocations that could fuel clashes in the region,” he added.
Moscow openly said on Thursday that it opposes deployment of NATO Patriot missiles on Turkey's border with Syria, a sign of deepening tensions across the region over the 20-month-old Syrian crisis.
“This would not foster stability in the region," Foreign Ministry spokesman Alexander Lukashevich said of Turkey's request to the Western military alliance for the deployment.
Turkey recently requested advanced PAC-3 model Patriots from NATO, which Germany, the Netherlands and the US have for intercepting ballistic missiles.
NATO said on Wednesday it will consider Turkey's request "without delay," and next week a NATO team will visit the alliance member for a site survey to consider a deployment.