The US, he said last week, would work to establish "interim zones of stability" in Syria to allow refugees to return home.
His words brought to mind the debates within the Obama administration about safe zones. Those would have involved patrols by US warplanes to deter the Syrian air force from bombing civilians and rebel forces.
President Trump, on the other hand, has promoted the notion of safe zones as a way to stop the tide of refugees pouring into Western countries, though without providing details.
Today a senior State Department official fleshed out the phrase a bit. He said the Americans had in mind pockets of stability in Syria's two conflicts: areas where coalition forces had defeated Islamic State militants, and areas where ceasefires could "de-escalate" the civil war.
The latter, he said, were being negotiated by Turkey, which backs some opposition groups, and Russia and Iran, which back the Syrian government, at talks in Astana, Kazakhstan.
He said the coalition would look for ways to reinforce any such areas of stability to make them safe for civilians, especially near the borders of critical allies: Jordan in the southwest, and Turkey in the northwest.
The official talked only of US humanitarian, not military support. But some sort of holding force would be necessary to secure the zones.
Recently America's top military officer in the Middle East, General Joseph Votel, said safe zones are a viable option in Syria where areas have been secured, but he didn't say who would secure them.
More likely he would have had US-trained forces rather than US troops in mind.
The coalition has had some success at stabilising areas liberated from Islamic State militants in Iraq, and wants to transfer that model to Syria.
But Syria is a much more complex war zone with no government partner, conflicts even between US allies, and peace talks bedevilled by collapsed ceasefire agreements.
So at this stage, the "interim zones of stability" are more of an idea than a plan.
Secretary of State Rex Tillerson has casually dropped a loaded phrase into the confusion about President Trump's plan for defeating the Islamic State Group.