But a crisis unfolding on the Syria-Turkey border that threatens to embroil the USA military in a wider regional conflict underscored how hard it will be for the relatively small US presence in Syria to influence the outcome of the conflict there.
"At present, these territories are under the control of the SDF, but the relationships between the Kurds and Arabs within the group are very tense and the U.S. announcement that the territory will be controlled by different groups under American leadership causes concern that the aim of the initiative is to divide Syria", Lavrov said.
In the crisis that is growing along the Turkish-Syrian border, the United States has said, the Syrian Kurdish fighters known as YPG, which were armed and supported by the US-led coalition are no longer part of the war on the Islamic State and receive no support. "By maintaining an American military presence in Syria until the full and complete defeat of ISIS is achieved, it will soon have two". "It is also essential so that IS can not reemerge in liberated and ungoverned areas", the Pentagon said.
Turkey and the United States, both allies in North Atlantic Treaty Organisation, were on the same side for much of Syria's civil war, both supporting rebels fighting to overthrow Syrian President Bashar al-Assad. Then the US shifted its focus to defeating the IS and establishing its influence in the country.
"I want to make clear that we'll judge the new government on its actions", she said. "Iran has dramatically strengthened its presence in Syria by deploying Iranian Revolutionary Guard troops; supporting Lebanese Hezbollah; and importing proxy forces from Iraq, Afghanistan, Pakistan and elsewhere".
"Instead, we will encourage worldwide assistance to rebuild areas the global coalition and its local partners have liberated", he said, referring to the SDF.
Squeezing Iran will, therefore, be one of the foremost goals of the continued USA troop presence in Syria, he said, acknowledging that the project will be hard.
"We're there to defeat ISIS", Tillerson said.
Much like with Iraq and Afghanistan, the United States can check out of Syria any time but it can never fully leave.
Erdogan on Tuesday reiterated that Turkey planned an imminent intervention in the Kurdish-controlled enclave of Afrin in northern Syria.
On Sunday the US -led coalition in Syria controversially announced it was working with the SDF - a group dominated by the terrorist PYD/PKK - to set up and train a Syrian border protection force.
The Pentagon acknowledged Turkey's concern over its plans for the security force.
On Monday, the Turkish President Recep Tayyip Erdogan said that his country is ready "at any moment" to start an operation in the besieged border area of Syria.
"Hey NATO! You are obliged to take a stance against those who harass and violate the borders of your members", Erdogan said.
As candidate, U.S. President Donald Trump was critical of his predecessors' military interventions in the Middle East and Afghanistan. "Currently, there are approximately 230 individuals training in the BSF's inaugural class, with the goal of a final force size of approximately 30,000", a spokesman for the US-led coalition, US Army Col. Ryan Dillon, told CNN in a statement. "We are not involved with them at all".
"We are not operating in Afrin".
The YPG is a major bone of contention in ties between Turkey and the United States, which considers it a key ally in fighting IS.