"We have for some time had conversations through intermediaries with the PYD," state department spokeswoman Jennifer Psaki told reporters at a daily news briefing Thursday, referring to the Syrian Kurdish Democratic Union Party (PYD).
"We have engaged over the course of just last weekend directly with the PYD," she said, adding the "brief conversation" took place outside the region, according to Xinhua.
The PYD's military wing is defending the border town of Kobane from attacks by the IS fighters. Pentagon spokesman John Kirby said Thursday that the extremists' advances "appear to have slowed" with intensifying US-led airstrikes.
Kirby told reporters that sandstorm had forced the US and its allies to reduce bombing on the IS in Iraq, enabling Washington to pool resources needed to hit more of the group's targets around Kobane in recent days.
He warned, however, that Kobane could still fall.
"We've all been honest about the fact that air power alone is not going to be able to save any town in particular," he said.
Psaki said Washington would not meet PYD's demand for weapons right now, noting "I don't think that we're at that point yet".