Earlier, 46 people were killed in a double car bombing in Homs
The US Secretary of State John Kerry says a provisional agreement had been reached with Russia on the terms of a ceasefire in Syria.
He said the cessation of hostilities could begin in the coming days.
A ceasefire was due to take hold on last Friday were dashed, but it collapsed amid increasing violence.
The announcement follows news that 46 people have been killed in two bomb blasts in the Syrian city of Homs.
According to the Britain-based Syrian Observatory for Human Rights, at least 28 civilians were killed when the car bombs exploded in the government-held city.
Images show massive damage to nearby buildings, wounded people, and charred debris.
A IS bomb attack in Homs last month killed 24 people, though the group has not claimed today's bombings.
Earlier, Syria's president, Bahsar al Assad, saaid he was ready to agree to a ceasefire - as long as what he called "terrorists" don't exploit it.
Opposition forces in the country have also agreed to a temporary truce, but only if Russia stops its air strikes in support of President Assad.