U.S. President Barack Obama has told Turkey's President Recep Tayyip Erdogan that it's critical to "finish the job" of securing Turkey's border with Syria.
The two leaders met on September 4 on the sidelines of the Group of 20 economic summit in Hangzhou, China.
Obama said securing the Turkish border was important because that is where would-be recruits to the Islamic State (IS) extremist group enter Syria.
Obama also said Turkey must not carry alone the burden of addressing the Syrian refugee crisis.
Meanwhile, Obama said talks with Russia would be key in reaching any deal to end hostilities in Syria but negotiations were difficult.
Obama told a news conference in Hangzhou that grave differences remained between Washington and Moscow.
"We're not there yet," Obama said. "I think it's premature for us to say there's a clear path forward, but there's the possibility at least for us to make some progress."
U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov have been deep in talks for weeks over a deal to boost U.S. and Russian military cooperation to fight IS and other extremists in Syria.
A possible deal could also include provisions to ensure aid can reach besieged areas of Syria and steps to prevent Syrian President Bashar al-Assad's government from bombing areas where U.S.-backed rebels are operating.
Obama’s meeting with Erdogan was their first since this summer's coup attempt.
The U.S. president said he condemned the attempted overthrow and would work with Turkey to help ensure that those responsible for an attempted coup are brought to justice.