Only way to save the Middle East country from 'endless bloodshed'.
Konstantin Zhuravlyov is missing for two weeks after crossing from Turkey into Syria.
'I've got to talk to my British colleague,' said the Russian president as he left a key fuel and energy session to take the phone call.
FSB say Konstantin Zhuravlyov, 35, is now back with his family in Tomsk after being held as a 'spy' by Syrian opposition.