Defeating Islamic State remains America's 'first priority' in Syria

Defeating the Islamic State group remains the top priority for the United States in Syria, even before stabilising the country, Secretary of State Rex Tillerson suggested.

Victory over the militant group would eliminate not only a threat to the US but to "the whole stability in the region," Tillerson told CBS television's 'Face the Nation' program in an excerpt released on Saturday.

The remarks come days after the US struck Syrian regime facilities for the first time since the war began, hinting at a shift in US policy in Syria.

"It's important that we keep our priorities straight. And we believe that the first priority is the defeat of ISIS," Tillerson said in a clip made public on the eve of the Sunday talkshow's air time.

"Once the ISIS threat has been reduced or eliminated, I think we can turn our attention directly to stabilising the situation in Syria," he said, using an alternative acronym for the militant group. 

"We're hopeful that we can prevent a continuation of the civil war and that we can bring the parties to the table to begin the process of political discussions."

But such talks would require the participation of Syrian President Bashar al-Assad's regime along with its allies, the former ExxonMobil chief executive noted, narrowing his focus on key Damascus ally Moscow, with whom Washington has particularly frosty relations.

"We're hopeful that Russia will choose to play a constructive role in supporting ceasefires through their own Astana talks, but also, ultimately, through Geneva," Tillerson said.

"If we can achieve ceasefires in zones of stabilisation in Syria, then I believe - we hope we will have the conditions to begin a useful political process."

The top US diplomat insisted he had no concerns about possible Russian retaliation following an unprecedented US strike on a Syrian airfield this week.

"The Russians were never targeted in this particular strike," Tillerson said. 

"It was a very deliberate, very proportional, and very targeted strike undertaken in response to the chemical weapons attack. And Russia was never part of the targeting."

The comments came as the US ambassador to the United Nations said there will be no peace in Syria while President Bashar al-Assad remains in power, in a statement that suggests the Trump administration could be closer to embracing regime change, CNN reported on Sunday.

"There's not any sort of option where a political solution is going to happen with Assad at the head of the regime," Nikki Haley told "State of the Union" program. 

"It just - if you look at his actions, if you look at the situation, it's going to be hard to see a government that's peaceful and stable with Assad."