MOSCOW (AFP) - Russian President Vladimir Putin on Thursday (March 24) took a keen interest in the briefcase of visiting US Secretary of State John Kerry, wondering aloud if it perhaps contained cash intended to sway his opinion on Syria's future.

"When I saw you getting off the plane and carrying your things, I got a bit upset," Putin began as the pair met for talks at the Kremlin where Kerry is set to try and shift the Russian leader's position on Syria's Bashar al-Assad.

"On the one hand, it's very democratic, on the other hand, I thought, things must be getting bad in the US," Putin said with a small laugh, "if there is nobody to help the Secretary of State with his briefcase".

"One would think it's all going well with the economy, no significant layoffs - but then I thought, maybe there was something in that briefcase that you could not entrust to anyone, something valuable.

"It must be money you brought, to better haggle with us on key issues," Putin joked, looking across the table at a smiling Kerry.

"When we have a private moment, I'll show you what's in my briefcase," Kerry replied.

"I think you will be surprised, pleasantly."

Quizzed by a journalist from a Russian state channel on the contents of the briefcase later at a press conference, Kerry made it clear the matter was not for public scrutiny.

"That's a secret between President Putin and me," he teased.