Kerry said he spoke in the morning with Russian foreign minister Sergey Lavrov to discuss terms of a ceasefire and the two now must reach out to the parties in the conflict.
He declined to go into the details of the agreement, saying it “is not yet done.”
But he said he hoped US president Barack Obama and Russian president Vladimir Putin would talk soon and that after that, implementation could begin.
“The modalities for a cessation of hostilities are now being completed,” Kerry said.
“In fact, we are closer to a ceasefire today than we have been. A cessation of hostilities... is possible over the course of these next hours.”
The Russian foreign ministry seemed to stop short of Kerry’s announcement.
The ministry said Lavrov and Kerry spoke on the phone for a second day in a row and discussed “the modality and conditions” for a ceasefire in Syria that would exclude groups that the UN Security Council considers terrorist organisations.
In Syria yesterday, a pair of explosions ripped through the city of Homs, killing at least 57 people, including 28 civilians, and wounding dozens, according to activists and Syrian state TV.