ST PETERSBURG, RUSSIA (AFP) - With a macho handshake, wide smiles for the cameras and a spot of small talk about the late summer weather, President Barack Obama and his Russian counterpart Vladimir Putin sought on Thursday to mask months of tensions that gave rise to talk of a bitter personal animosity.

The squirmingly awkward pictures from their last encounter at the G-8 in June and Mr Obama's cancellation of a bilateral summit in Moscow had created expectations of another tense encounter. But the two men made some effort to show that - if not exactly the best of friends - they could still make a show of diplomatic bonhomie when required.

Mr Obama's armoured vehicle was among the last to arrive to be welcomed by Mr Putin for the start of the G-20 summit outside St Petersburg. Unusually, the car - known as "the beast" - arrived with both the American and Russian flags on its bonnet in a possible US gesture towards the host.

Mr Putin stood alone with his hands behind his back as he waited to welcome his guest to the Konstantinovsky Palace on the Gulf of Finland under gleaming blue early September skies. Mr Obama strode purposefully out of the car, arm extended in greeting towards his Russian host.

In a brief encounter, they shook hands and swopped some words possibly about the glorious late summer weather. They managed gaping smiles for the hordes of media waiting for the slightest hint of tension, with Mr Obama producing his trademark grin as if to order before giving Mr Putin a pat on the shoulder. It was hardly an emotional reunion after months apart, but did not appear to exude venom either.

The pro-Kremlin newspaper Izvestia this week said Mr Obama and Mr Putin, who would normally sit next to each other at the grand dinner according to alphabetical order, would be seated apart. No bilateral meeting is scheduled between the pair, but officials have left the door open to a less formal exchange during the course of the summit.

Mr Putin also announced that after requests by "some participants", the crisis in Syria would after all be discussed over Thursday's dinner, something that would gladden Mr Obama.

Mr Obama travelled to the G-20 despite cancelling a planned bilateral summit in Moscow that was scheduled this week after relations reached a new post-Cold War low. Rows over the conflict in Syria, Russia's awarding of asylum to US intelligence leaker Edward Snowden and tough laws passed by the Russian Parliament have all caused deep tensions.

The two looked deeply ill at ease when they last met in Northern Ireland at the G-8 summit in June, with pictures showing the two men making no eye contact and Mr Putin slumped in his chair looking distracted. That prompted Mr Obama to later admit that his Russian counterpart sometimes looked like "the bored kid at the back of the classroom". It also sparked speculation among many analysts that the pair have a dire personal rapport, but Mr Putin denied this in a television interview on Wednesday, describing Mr Obama as "business-like and interesting".

This is only Mr Obama's second visit to Russia as president, which in itself shows the state of US-Russia relations. He visited Moscow in July 2009 for talks with Mr Putin's predecessor Dmitry Medvedev, agreeing significant arms reductions and establishing a genuinely warm personal rapport with the then leader.

However, when Mr Putin returned to the Kremlin after the 2012 elections, Mr Medvedev took on the less powerful post of prime minister and a "reset" in relations went back to square one.

Mr Obama hardly endeared himself to Mr Putin in 2009 when ahead of his trip to Russia he described the Russian strongman as having "one foot in the old ways of doing business".

Relations between Mr Putin and Mr Obama are "the type of relations that should exist between two leaders that share responsibility" for world security, Mr Putin's spokesman Dmitry Peskov said.

The relations are "rather constructive though lately they have had quite serious disagreements", he admitted.