Russia said it would not permit a no-fly zone to be implemented over Syria, following reports that plans for such a measure were being drawn up by the United States.
"We saw with the example of Libya how such a zone is introduced and how such decisions are implemented. We do not want a repeat of this in respect to the Syria conflict. I think that we will not permit in principle such a scenario," Russian foreign ministry spokesman Alexander Lukashevich told reporters.
Russia effectively allowed western powers led by the United States to deploy a no-fly zone over Libya in 2011 by deciding not to veto a UN Security Council resolution authorising such a move.
But Russia responded with anger when the same resolution was used to justify the bombing of ground positions of troops of the late Libyan dictator Moamer Kadhafi -- a Moscow ally from Soviet times.
Foreign minister Sergei Lavrov said on Saturday that a no-fly zone over Syria -- another key Moscow ally in the Middle East -- would be "illegal".
But he did not at the time go so far as to suggest that Russia would block any UN Security Council resolution for a Syrian no-fly zone.
US media reports that Washington was preparing to enforce a no-fly zone over Syria, were fuelled over the weekend by the Pentagon's confirmation that it will keep F-16 fighters and Patriot missile interceptors in Jordan, after the end of a joint military exercise there this month.
A US defence official said last week the military would also keep a unit of US Marines on amphibious ships off the Red Sea coast after consultations with Jordan.
The Wall Street Journal had earlier reported that the no-fly zone could be deployed from Jordan over the western sections of Syria.
The Russian ministry spokesman said US activities in Jordan "are also a direct violation of international law."