Kerry said the Obama administration remains committed to defeating ISIS, to containing the Syrian conflict within that country's borders and "intensifying" diplomatic efforts to end the Syrian civil war, which he said has been a "central concern" of the U.S. government.
Kerry's speech at the U.S. Institute of Peace comes as the White House has faced a steady stream of criticism from Republicans and other critics accusing the administration of lacking a strategy to defeat ISIS and quell regional turmoil.
In comments aimed at those who say the U.S. has done too little, Kerry touted the progress of the U.S.-led coalition in bombing ISIS targets over the last 14 months -- pointing to the ouster of ISIS from the Syrian border town of Kobani and the Iraqi city of Tikrit, the killing of top ISIS leaders and the humanitarian mission that helped save members of the Yadizi minority under threat from ISIS last summer.
But Kerry primarily focused on the need to make headway on the diplomatic front, where the U.S. has struggled to move the ball forward on transitioning Syrian President Bashar al-Assad from power and creating a more inclusive government.
"The truth is that nothing would do more to bolster the fight against the terrorists than a broadly supported diplomatic process that would begin to de-escalate the conflict, and that would give the Syrian people a real choice -- not between Assad and Daesh -- but between the status quo and something," Kerry said, using another name for ISIS.
Parties to the negotiations -- which include the U.S., Russia and several European and Middle Eastern countries -- last met in Vienna in October, emerging with a communiqué that laid out areas of agreement on resolving the Syrian conflict.
"It is precisely through this political process that we can, for the first time, marshal the support of the entire international community against a single common enemy -- Daesh," Kerry said.
Still, the secretary of state acknowledged the difficulties the U.S. faces in convincing Syria's top allies Russia and Iran that Assad must go, saying that "we are still working through with Russia and Iran the question of Assad and his role."
While U.S. leaders have long stated that Assad cannot be allowed to remain in power, Kerry and other U.S. officials have softened their tone on the matter in recent weeks -- suggesting instead that Assad has no place in Syria's "long-term future" but leaving the door open for him to stay around during a longer transition period.
Kerry simply stated Thursday that the U.S. and its allies believe that "neither peace nor the defeat of Daesh is possible with Assad in power."