In the midst of the US administration’s attempt to ram through the American Congress a resolution authorizing the use of military force against Syria, President Barack Obama arrived in Sweden Wednesday en route to a G-20 summit that will likely be overshadowed by the impending war.

Obama’s bid for international support for US military aggression against Syria appeared to be gaining little ground as he headed to the summit in St. Petersburg, Russia.

At a news conference in Stockholm Wednesday, Obama declared in relation to the alleged use of chemical weapons in Syria, “I didn’t set a red line. The world set a red line.” He continued, “My credibility’s not on the line. The international community’s credibility is on the line.”

These rhetorical flourishes, disassociating himself from remarks he made over a year ago declaring that any use of chemical weapons in Syria would be a “red line” that would invoke a US response, were particularly unconvincing. Republicans in Washington charged him with shirking his responsibility for the proposed military action, while the majority of European governments formally maintain that such a line would have to be drawn by the United Nations.

This attitude has solidified in the wake of last week’s stunning reversal for Obama’s principal international ally, British Prime Minister David Cameron, who lost a vote in parliament supporting military action and subsequently announced that his government would not participate in a US-led attack on Syria.

Obama faces opposition from the host of the G-20 summit, Russian President Vladimir Putin. On the eve of the US president’s arrival, Putin dismissed American allegations of the Syrian regime’s use of chemical weapons as “unimaginable nonsense” and condemned any US military action as illegal aggression.

In advance of the summit, Washington canceled a planned bilateral meeting between Obama and Putin in retaliation for Russia’s granting of political asylum to Edward Snowden, the former National Security Agency (NSA) contractor who disclosed massive illegal spying operations against the people of the US and the world.

The NSA spying revelations are also expected to cast a pall over the G-20 proceedings, following reports that world leaders attending previous summits were subjected to electronic eavesdropping by the US spy agency.

In an interview with the Associated Press and Russia’s Channel 1 released Wednesday, Putin derided a declassified US intelligence report containing unproven assertions of the Syrian regime’s responsibility for an alleged use of chemical weapons outside of Damascus on August 21, the pretext invoked to justify a US assault on Syria.

“From our viewpoint, it seems absolutely absurd that the armed forces, 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 forbidden chemical weapons while realizing quite well that it could serve as a pretext for applying sanctions against them, including the use of force,” said the Russian president.

The alleged chemical attack took place on the very day that UN weapons inspectors invited into Syria by the regime of President Bashar al-Assad began their work.

Russian Foreign Minister Sergey Lavrov stated that Washington had provided Moscow with the same declassified report, and when asked to substantiate its claims with evidence was told that the information was “classified.”

“There are no supporting facts, there is only repetitive talk in the vein of ‘we know for sure,’ said Lavov. “And when we ask for further clarification, we receive the following response: ‘You are aware that this is classified information, therefore we cannot show it to you.’ So there are still no facts.”

The Russian government on Wednesday issued its own 100-page intelligence report to the United Nations based on samples gathered by Russian experts at the scene of the March 19 chemical weapons attack on the northern Syrian town of Khan al-Assal, near Aleppo, in which 26 people, the majority of them Syrian soldiers, died.

Based on an analysis of the chemicals and the rocket used to deliver them, the report concluded that the attack was carried out by the Western-backed militias operating inside Syria.

“It was determined that on March 19, the rebels fired an unguided missile Bashair-3 at the town of Khan al-Assal, which has been under government control,” Russia’s ambassador to the United Nations, Vitaly Churkin, stated. “The results of the analysis clearly show that the shell used in Khan al-Assal was not factory made and that it contained sarin.” The chemical analysis, he said, demonstrated that it was not “a standard chemical charge” found in weapons in the hands of government forces.

Washington has dismissed the extensive evidence that the so-called “rebels” are in possession of chemical weapons and have used them, as it cuts across the pretext it has manufactured to prosecute a war for regime-change.

The Russian Foreign Ministry also called for the UN’s International Atomic Energy Agency to urgently prepare an analysis of the potential risk posed by US air strikes hitting a small nuclear reactor near Damascus, warning that the “the consequences could be catastrophic.”

Speaking in Moscow on Wednesday, Putin warned against a unilateral US attack, stating that “anything that is outside the UN Security Council is aggression, except self-defense. Now, what Congress and the US Senate are doing in essence is legitimizing aggression. This is inadmissible in principle.”

He also branded US Secretary of State John Kerry a “liar” for his testimony before a Senate committee on Tuesday. Asked by a senator whether it was not true that the so-called “rebels” had “become more infiltrated by Al Qaeda over time,” Kerry responded “No, that is actually basically not true. It’s basically incorrect.”

At a meeting in the Kremlin Wednesday, Putin commented: “They lie beautifully, of course. I saw debates in Congress. A congressman asks Mr. Kerry: ‘Is Al Qaeda there?’ He says, ‘No, I am telling you responsibly that it is not.’”

Putin continued: “Al Qaeda units are the main military echelon, and they know this. It was unpleasant and surprising for me—we talk to them, we proceed from the assumption that they are decent people. But he is lying and knows he is lying. It’s sad.”

Russian Television (RT) reported Wednesday that Syrian protesters have gathered at key military sites, offering themselves as “human shields” against a US attack. Demonstrators set up a camp at the foot of Qasioun Mountain outside of Damascus, the location of a number of key military facilities.

One of the protesters told RT, “We are here to express our loyalty to our country in the face of American threats. We don’t want what they did in Iraq over chemical weapons to be done in our country.”