President Barack Obama said Thursday that Islamic State could be defeated only if there was a political agreement in Syria.
"It's going to be a multiyear task and we're not going to be able to fully succeed in eliminating their safe havens until we have a political settlement of some sort in Syria," the president said at an Asia-Pacific conference in the Philippines.
Obama also previewed the soon-to-be-initiated global peace conference on Syria. He said the talks could identify opposition groups that can be part of a transitional government and set out a blueprint for new elections.
The next step, he said, would be "to initiate a cease-fire that may not be observed by everyone, but at least would create pockets of calm that could hopefully grow over time."
One thing is for sure in Syria's future, Obama said: There can be no place for President Bashar al-Assad.
"It is unimaginable that you can stop the civil war there when the overwhelming majority of people in Syria consider him to be a brutal, murderous dictator," the president said. "He cannot regain legitimacy."
The international community has been working for more than three years to find a way to end the fighting in Syria, which has killed at least 250,000 people. Assad's role has divided key members on either side of the conflict.
Obama said Russia and Iran have to decide whether to continue to prop up Assad or work with the international community to save the Syrian state.
Assad told Italian state television that no talks to end the war could begin while "terrorists" occupied parts of Syria. He uses the word "terrorists" to refer to all opposition, from moderates to Islamic State extremists.
Also Thursday, Saudi Arabia announced it would hold a conference next month to try to unite the moderate Syrian opposition groups ahead of the international peace talks. It gave no details.
Campaign against IS
Deputy national security adviser Ben Rhodes told reporters earlier Thursday that Obama was using his overseas trip to build more support for fighting the militant group that has claimed attacks in a number of countries in recent weeks.
"[World leaders] understand that this is not something that is distant, this ISIL group has aspirations to attack the entire civilized world," Rhodes said, using another acronym for Islamic State. "So there is a new sense of urgency. We want to take that urgency and make it concrete."
The U.S. has been leading a coalition of nations carrying out airstrikes against the militants in Syria and Iraq for more than a year.
Canada has been among those with warplanes bombing targets in both countries, but is now withdrawing from that mission.
Prime Minister Justin Trudeau promised during a campaign that brought him to power this month that he would withdraw the six Canadian fighter jets in the region, and reiterated his commitment to that pledge Thursday.
"We will be doing that in collaboration, coordination with all our allies to ensure that the coalition still has tremendous impact against ISIL," he said.