President Barack Obama was greeted on arrival at the St. Petersburg G20 summit Thursday with a warm handshake from Vladimir Putin and an exchange of joking comments about the fine weather. Opening the summit, Putin said the overriding issue, Syria, would be discussed over dinner. The US president had just heard the European Union delegation state that Syrian crisis must only be solved by diplomatic means. Thenb, too, President Dilma Rousseff of Brazil cancelled her planned trip to Washington inangry response to the revelation by Edward Snowdon that US intelligence had eavesdropped on her calls. Obama has scheduled a meeting on the summit sidelines with French President Francois Holland who remains committed to backing US military action against the Assad regime’s use of chemical weapons.