In speeches at the United Nations General Assembly on Monday, Russia’s Vladimir Putin and President Barack Obama indicated a vague alignment on defeating “terrorism” in Syria, but butted heads on just about every aspect of the intractable war there — who should lead the fight against the Islamic State in Iraq and the Levant (ISIL), what the international community’s long-term goals should be and who is ultimately to blame for four years of unrelenting bloodshed.

The addresses set a combative tone before a 95-minute meeting between the two leaders later on Monday — their first face-to-face discussion in a year — at which they discussed Russia’s military buildup in support of Syrian President Bashar al-Assad’s regime and recent reports that Moscow intends to launch its own coalition against ISIL, separate from the U.S.-led airstrikes.

A U.S. official said Obama and Putin agreed to discuss a political transition in Syria, but remain at odds about what that would mean for Assad's future. The official insisted on anonymity because the official was not authorized to publicly discuss the private meeting.

The official said Obama reiterated to Putin that he does not believe there is a path to stability in Syria with Assad in power. Putin has said the world needs to support Assad because his military has the best chance to defeat Islamic State militants.

The official said Obama and Putin's 90-minute meeting was dominated by discussions of the crises in Syria and Ukraine, with each consuming about half the discussion.

After the meeting, Putin said the United States is taking part in efforts to settle the Ukrainian crisis, and that Washington was working with the Ukrainians and the Europeans to maintain diplomatic contacts with Russia to help with a settlement.

He called the talks were "very constructive, business-like and frank."

Putin said Russia has not ruled out joining air strikes against the Islamic State in Syria but would not send ground troops into combat. "We are thinking about it, and we don't exclude anything."

Before meeting Obama, Putin in his first speech at the General Assembly in a decade, had said, “We must join efforts to address the problems that all of us are facing on the basis of international law and create a genuinely broad international coalition against terrorism. ... Similar to the anti-Hitler coalition, it could unite a broad range of forces that are willing to resolutely resist those who, just like the Nazis, sow evil and hatred of humankind.”