Also differences over the Syrian crisis between the US and the Russian leaders remain deep, Barack Obama and Vladidmir Putin said the two men agreed that violence might be stopped in the conflict-hit country.

Also differences over the Syrian crisis between the US and the Russian leaders remain deep, Barack Obama and Vladidmir Putin said the two men agreed that violence might be stopped in the conflict-hit country.

The US and Russian presidents faced off on the sidelines of the G8 summit in Northern Ireland, days after the White House signaled it would begin arming foreign-backed militants fighting the Syrian government.

Putin and Obama did not try to disguise the fact they are estranged on Syria and cannot agree on Syrian President Bashar al-Assad's fate, but appeared keen to keep flagrant differences on the vicious crisis from sinking wider US-Russia relations.

They announced Obama would go to Moscow on September 3-4 for a full-scale summit, expanding a previously announced trip that includes the G20 summit in St Petersburg.

"Of course our opinions do not converge, but all of us have the intention to stop the violence in Syria and stop the growth in the number of victims," said Putin.

He said he and Obama agreed that the vicious civil war that has killed at least 90,000 people according to the United Nations must end "peacefully" and through talks.

"We agreed to push the parties to the negotiating table."

Obama acknowledged that they had "different perspectives". But the session ended with a firm handshake, after the US president made a gentle joke about the Russian leader's prowess in judo and his own declining basketball skills.

Washington and Moscow have agreed in principle to host a conference in Geneva on ending the violence in Syria, but the timetable for the meeting has continually slipped over disagreements on who should attend.