Mark N. Katz is a professor of government and politics at George Mason University. He is the author of "Leaving Without Losing: The War on Terror After Iraq and Afghanistan" (Johns Hopkins University Press, 2012). Follow his blog.

(CNN) -- At the Group of 20 summit in Mexico, President Barack Obama and Vladimir Putin had their first face-to-face meeting since Putin resumed the Russian presidency in May. The joint statement they issued afterward indicated several issues (including Iran and Syria) that the two sides would seek to cooperate on, but it did not announce any significant agreements to do so.

More telling were the visual images when the two presidents were together; Obama appeared to be doing his best to project an image of warmth and friendliness, while Putin was stiff and reserved, as he usually is with other world leaders. It appeared that Obama was earnestly seeking to befriend Putin, but Putin was not reciprocating.

Why would Putin behave this way? It may be because, unlike Obama, he may not be looking for opportunities to cooperate, nor be embarrassed about forgoing them. He appears to have a much more transactional approach to foreign policy, running something like this: Washington wants Moscow to adopt the American approach to Iran and Syria and several other issues. But it is unwilling to make concessions to Moscow to get it....