ANTALYA, Turkey --?US President Barack Obama and Russian President Vladimir Putin, meeting on the sidelines of the G20 leaders' summit here on Sunday, agreed on a political transition in Syria.

In an informal meeting across a coffee table that lasted about 35 minutes, the two leaders exchanged ideas on the conflicts in Syria and eastern Ukraine.

The United States, Russia and regional powers agreed a day earlier on the timetable of establishing a transition government in Syria and holding an election within 18 months, but failed to bridge gaps over the future of Syrian President Bashar al-Assad.

"President Obama and President Putin agreed on the need for a Syrian-led and Syrian-owned political transition, which would be preceded by UN-mediated negotiations between the Syrian opposition and regime as well a ceasefire," a White House official told reporters after the meeting.

Obama once again called for the implementation of the Minsk agreement, a deal that seeks to end the bloodshed in Ukraine's east, the White House official added.

Yuri Ushakov, Putin's advisor on foreign affairs, told reporters that Putin and Obama focused on Syria in their conversation, and also talked about the series of terror attacks that hit Paris on Friday night and left at least 129 people dead.

He said the two leaders shared strategic goals in terms of fighting the Islamic State, but differed on tactics.

The United States will work with France to intensify air strikes on the Islamic State in Syria and Iraq, said Benjamin Rhodes, Obama's deputy national security advisor.