UNITED NATIONS • Russia and the United States have agreed to look for a diplomatic end to the Syrian civil war, but clashed over the central question of whether Syrian President Bashar al-Assad should retain power.

During a 90-minute meeting on Monday, US President Barack Obama and Russian President Vladimir Putin agreed that their armed forces should hold talks to avoid coming into conflict in Syria after a Russian military build-up there over the past several weeks.

Mr Putin later said the discussions had been "very constructive, business-like and frank". However, he added that "relations between Russia and the United States are unfortunately at a pretty low level".

Speaking after his meeting with Mr Obama, Mr Putin told reporters Russia was pondering what more it could do to support Syrian government and Kurdish forces against Islamic State in Iraq and Syria (ISIS) militants.

"We are mulling over what we would really do extra in order to support those who are in the battlefield, resisting and fighting with terrorists, ISIS first of all," he said.

A senior US official, speaking on condition of anonymity, told reporters after the meeting: "The Russians certainly understood the importance of there being a political resolution to the conflict in Syria, and there being a process that pursues a political resolution."

Earlier in the day, relations between the two leaders appeared frosty - they clinked glasses at a lunch, but Mr Obama had a piercing look as Mr Putin smiled - and they laid out starkly differing positions on Mr Assad in their addresses before the annual United Nations General Assembly gathering of world leaders.

In his speech to the UN, Mr Putin suggested there was no option but to work with Mr Assad, a long-time ally of Russia.

REUTERS, AGENCE FRANCE-PRESSE, BLOOMBERG, NEW YORK TIMES