You could tell by the G20 meeting Obama was softening Brown up for a favour.
No need to soften Brown up for a favour, all our politicians are putty in the American's hands. Perhaps things would be different if their family had persons in the military, or perhaps if they themselves had some experience.
You don't get the French or the Germans willing to put the lives of their young men at risk.
Since Russia has already had a go at Afghanistan, and Obama is warming to the Ruskies, why doesn't he ask them to send in troops?