WASHINGTON (AFP) - The White House hit back on Thursday at Russian President Vladimir Putin's dismissal of "American exceptionalism", saying that, in contrast to Moscow, Washington is a supporter of human rights and freedom of speech.

As United States and Russian negotiators discuss securing and destroying Syria's chemical weapons, spokesman Jay Carney Moscow was "isolated and alone" in accusing the opposition of a poison gas attack that Washington claims killed 1,400 civilians.

In an opinion piece published in the New York Times Wednesday, Mr Putin argued that Syrian rebels were behind the deadly Aug 21 attack on the outskirts of Damascus, suggesting they did so to provoke foreign military intervention in their favour.

The Russian leader also took a swipe at remarks US counterpart Barack Obama made in a somber national address on the situation in Syria earlier this week.

"I would rather disagree with a case he made on American exceptionalism, stating that the United States' policy is 'what makes America different. It's what makes us exceptional.' It is extremely dangerous to encourage people to see themselves as exceptional, whatever the motivation," Mr Putin wrote.

Mr Carney said the US wasn't surprised by the comments.

"But the fact is that Russia offers a stark contrast that demonstrates why America is exceptional," he added. "Unlike Russia, the United States stands up for democratic values and human rights in our own country and around the world and we believe that our global security is advanced when children cannot be gassed to death by a dictator."

Mr Carney said it was "worth pointing out there's a great irony in the placement of an op-ed like this, because it reflects the truly exceptional tradition in this country of freedom of expression".

"And that is not a tradition shared in Russia, by Russia, and it is fact freedom of expression has been on the decrease over the past dozen or so years," he added.