United States' military action against Syria without the United Nations' approval would represent an act of “aggression,” Russia’s President Vladimir Putin has said.

In a wide-ranging interview to Russian state television and Associated Press aired on Wednesday, Mr. Putin said he did not exclude supporting the use of force against Syria at the United Nations if there was “objective, precise evidence” proving that the Syrian Government was behind the use of chemical weapons. But he strongly warned Washington against launching unilateral attack against Syria.

“In line with international law, the U.N. Security Council alone can sanction the use of force against a sovereign State. Any other pretext or method to justify the use of force against an independent sovereign State is inadmissible and can only be qualified as aggression,” Mr. Putin said.

The Russian leader reiterated his view that it would be “absurd” for the Government of President Bashar al-Assad to resort to chemical weapons at a time when the tide of war was swinging its way.

“From our viewpoint, it seems utterly absurd that the regular armed forces, which are on the offensive today and in some areas have encircled the so-called rebels and are finishing them off, that in these conditions they would start using banned chemical weapons while realising quite well that it could serve as a pretext for applying sanctions against them, including the use of force,” Mr. Putin said.

Evidence of poisonous gas attacks must be “convincing” and should not be based on “rumours” or “eavesdropping” by secret services, he added.

Mr. Putin compared the evidence presented by Washington to the notorious “anthrax” vial Secretary of State Colin Powel showed in the U.N. General Assembly to justify the 2003 invasion of Iraq.

“All these arguments turned out to be untenable, but they were used to launch military action, which many in the U.S. called a mistake. Have we forgotten it? ... I assure you, we have not. Everybody remembers it and factors in in their decision,” Mr, Putin said.

The Russian President, who will host the G20 summit in St. Petersburg on Thursday, said he would raise the Syrian crisis issue at the summit.

Mr. Putin, a former career officer in the Soviet KGB, refused to disclose what Russia would do if the U.S. attacked Syria.

“We have our ideas about what we will do and how we will do it, in case the situation develops toward the use of force or otherwise,” he said. “We have our plans, but it’s too early to talk about them.”

Mr. Putin confirmed that Russia had a standing contract to supply the S-300 air defence missile system to Syria and had already delivered “some components” before the deal was “suspended.”

“But if we see that steps are taken that violate the existing international norms, we shall think how we should act in the future, in particular regarding supplies of such sensitive weapons to certain regions of the world,” he said.

Three years ago, Russia cancelled a contract to sell the S-300s to Iran under strong U.S. pressure, but last month, Moscow reportedly offered Tehran to supply a still more powerful system - Antey-2500.

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