The US will continue to pursue the Obama administration's five-pronged approach of using military force; identifying and intercepting terrorist fighters who go to Syria from other countries; targeting the terror group's finances; working to counter its propaganda; and stabilizing areas once ISIS has been ousted.
Tillerson, speaking as he opened the 10th Global Coalition Ministerial meeting on ISIS, added that "the United States will increase our pressure on ISIS and al-Qaeda and will work to establish interim zones of stability, through ceasefires, to allow refugees to return home."
He offered no details, but said the US is "working to tailor a similar approach specific to the challenges in Syria" and that it would be "a more refined approach" that it "is still coming together."
The Obama administration had hesitated to establish "safe zones" because of the military commitment required to defend such areas from Syrian government forces and the possibility of a clash with Russian forces, present in the country to help bolster its ally, the Syrian regime.
"I recognize there are many pressing challenges in the Middle East, but defeating ISIS is the United States' No. 1 goal in the region," Tillerson said. "When everything is a priority, nothing is a priority. We must continue to keep our focus on the most urgent matter at hand."
Diplomats said they're eager for the administration to clarify its strategy. "I was hoping for more specifics," French Foreign Minister Jean-Marc Ayrault told reporters. "We've been asking for specific answers for a couple of weeks from the new administration."
"I acknowledge it takes time for the American administration to consider the decisions," the French minister said. "But we have our own ideas and we need to move forward."
Ayrault said that top Trump officials told him they needed "a bit more time to consider their options" and that they would present them to the President in the next few weeks.
A senior Arab diplomat said the day's meeting was being seen as more of "a briefing" than an unveiling of any plan -- and that there clearly isn't one in place yet.
"The administration is saying the right things, but the broader strokes have not morphed into a strategy yet," the diplomat said. "Right now it's about short-term tactical moves. Any strategy has to take into account how you confront all of the extremists in the region and how to confront Iran."
The Arab envoy said expectations for the Trump administration weren't high.
"We don't expect a brand new or fundamentally different strategy," the diplomat said, adding that one change foreign partners do anticipate is a faster decision-making process.
"There won't be as much debate about every decision," the diplomat said of the new administration. "(Defense Secretary James) Mattis and the generals will tell Trump what they think they need to do and Trump will approve it. Everything will be expedited."
But Ayrault hasn't seen the process speed up. "There are is some American hesitation as to which forces should be used," he said, referring to the militias on the ground, which are allied with different interests and ethnic groups. He said the US also needs to firm up its approach to taking back Raqaa, the ISIS stronghold in Syria.
He also called for more American direction on peace talks being organized by the UN in Geneva, and he said it wasn't clear to him what Tillerson meant by "interim zones of stability."
The 68-member coalition focused the one-day meeting, hosted at the State Department, on the ground campaign in Iraq and Syria, as the US backs local Iraqi forces fighting to retake the ISIS stronghold of Mosul and is expanding its effort as it pressed toward the terror group's capital of Raqqa, in Syria.
The group also concentrated on raising funds to support humanitarian efforts to stabilize areas liberated from ISIS. Despite Trump administration proposals to slash the State Department budget -- and particularly its aid and development programs -- funding to help stabilize areas affected by ISIS should not be affected, State Department spokesman Mark Toner has said, as it has already been allocated in previous budgets.
Wednesday's event marked the first full meeting of the coalition since 2014 and the first of the Trump administration. President Donald Trump campaigned on a promise to take a tougher stance against ISIS.
As a candidate, Trump announced he had a secret plan to defeat ISIS, even as he was suggesting that the US needed to pull back from acting as a world policeman and enforcer of stability. Instead of unveiling that secret plan after he was elected, Trump signed an executive order on January 28 directing his national security team to come up with a strategy to defeat the group.
On Wednesday, Tillerson made clear the administration's plan will rely heavily on military means. "The expansion of ISIS has necessitated a large-scale military response, and our offensive measures are reclaiming areas in Iraq and Syria in which ISIS has had a large and destructive footprint. Our end goal in this phase is the regional elimination of ISIS through military force."
Tillerson also gave a nod to restabilizing areas once ISIS is defeated. He referred to efforts to clear rubble and land mines, restore water services and electricity. "A successful stabilization phase will set the stage for a successful normalization phase," the US diplomat said.
"We will continue to facilitate the return of people to their homes, and work with local political leadership," he told the gathering. "They will provide stable and fair governance, rebuild infrastructure, and provide essential services. We will use our diplomatic presence on the ground to facilitate channels of dialogue between local leadership and coalition partners."
But he also said that "we are not in the business of nation-building or reconstruction."
Once areas are stabilized, he continued, "local leaders and local governments will take on the process of restoring their communities in the wake of ISIS with our support."
Tillerson called on the gathered nations to do more to contribute to the fight, both on the military and humanitarian front. He noted that the US provides 75% of the military resources in Syria and covers 25% of humanitarian aid.
"The United States will do its part," Tillerson said, "but the circumstances on the ground require more, from my point of view," of other coalition members.
Many former generals, including some who fought in Iraq, have warned that the US ability to do that work could be endangered by the budget cuts Tillerson is charged with implementing at the State Department.
"If we've learned anything since September 11 from the military side, it's that the challenges we face today don't necessarily lend themselves to pure military solutions," retired four-star General George Casey, the former commanding general in Iraq from 2004 to 2007, told CNN this week.