US and Russia relations 'stuck in a trough'
4 September 2013 Last updated at 07:11 BST
President Putin and President Obama should have been meeting in Moscow on Wednesday, ahead of this week's G20 meeting in St Petersburg.
But the meeting was cancelled in July when Russia granted political asylum to the American whistle-blower Edward Snowden.
The latest Syrian crisis has strained the relationship further.
For the latest in the BBC's series on Putin's Russia, Daniel Sandford looks at the current relationship between the Cold War rivals.