Putin Puts Pressure on U.S. to Release Proof of Syrian Chemical Attacks

U.S. Will have to be as open with Russia as it is with Congress to prove point.

"There are experts who believe that the evidence presented by the [Obama] administration doesn't look convincing," Russian President Vladimir Putin said of reported chemical weapons attacks in Syria.

"There are experts who believe that the evidence presented by the [Obama] administration doesn't look convincing," Russian President Vladimir Putin said of reported chemical weapons attacks in Syria.

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Remarks from Russian President Vladimir Putin before hosting a major international summit in his country do little to shift the predicament facing the United States, tasked with finding international support for a military strike on Syria.

[READ: U.S. Has Lost Tactical Advantage in Syria, Experts Say ]

In an interview released Wednesday, Putin expressed willingness to back President Barack Obama's request to launch missiles at Syria on the condition that there is clear and convincing evidence presented to the United Nations that the Assad regime used chemical weapons. Barring such proof, he warned that Russia has its own ideas for what it would do following a U.S. unilateral strike.

The former KGB officer's criticisms of what the U.S. is considering in Syria were mirrored on Capitol Hill on Tuesday and Wednesday, where lawmakers questioned Secretary of State John Kerry's pleas for authorizing a military strike.

"The Assad regime, and only undeniably the Assad regime, launched a chemical attack," Kerry told the Senate Foreign Relations Committee Tuesday, saying suspicions that the attacks were staged by the opposition to gain international support are "only the most willful desire to avoid reality."

Kerry declined to specify on the intelligence that lead to such certainty, opting instead to brief the lawmakers during a closed-door classified session Wednesday morning.

"If there is evidence that chemical weapons have been used, and used specifically by the regular army, this evidence should be submitted to the U.N. Security Council," said Putin in an interview with the Associated Press prior to hosting a G-20 Summit in St. Petersberg. "And it ought to be convincing. It shouldn't be based on some rumors and information obtained by intelligence agencies through some kind of eavesdropping, some conversations and things like that."

Putin hinted that Russia might continue incomplete shipments of S-300 missile parts to Syria – which he says is "a very efficient weapon" for air defenses – if the U.S. moves forward with the air strikes.

"There are experts who believe that the evidence presented by the [Obama] administration doesn't look convincing," he said, "and they don't exclude the possibility that the opposition conducted a premeditated, provocative action trying to give their sponsors a pretext for military intervention."

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A former top diplomat to Russia says Putin's rhetoric has created a very difficult situation for the U.S. to prove its point on the international stage.

"He puts a very high bar on what it would take to have Russia reverse that position," says James F. Collins, who served as U.S. ambassador to Russia from 1997 to 2001. "In some ways, maybe for the first time, Mr. Putin is being open to the use of force in certain circumstances, but those circumstances are very tough."

"His discussion of the delivery or non-delivery of the S-300 missiles is implicitly, directly linked to this question about what's happened on chemical weapons," adds Collins, now the Russia program director at the Carnegie Endowment. "This is an implicit warning here, that right now the anti-aircraft system is on hold, but you should not take that for granted if there is a unilateral action by the U.S. against Syria."

Putin went on in his interview to dismiss media reports that he and Obama have a chilly relationship, forged from public events where both leaders appear disinterested and specific instances such as Russia's decision to harbor leaker Edward Snowden.

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Collins says this is likely an attempt to seize the moral high ground going into the G-20 negotiations. It establishes a tone that the Russian government is reasonable and open to new ideas.

"It is, in some ways, a contrast to some of the pretty nasty things he's been saying, pretty contemptuous things he's been saying about the U.S. over the last several months, and particularly regarding Syria," says Collins, adding, however, that Russian leaders likely believe there is no evidence they will see that will change their mind.