AMMAN/BEIRUT - US Secretary of State John Kerry said on Sunday he and his Russian counterpart, Sergei Lavrov, had reached a provisional agreement on terms of a cessation of hostilities in Syria and the sides were closer to a ceasefire than ever before.

Meanwhile, violence continued to rage in Syria. Multiple bomb blasts in a southern district of Damascus killed at least 87 people on Sunday, the Britain-based Syrian Observatory for Human Rights said, and twin car bombs killed at least 59 people in Homs, the monitoring group said.

Assad said on Saturday he was ready for a ceasefire on condition "terrorists" did not use a lull in fighting to their advantage and that countries backing the insurgents stopped supporting them.

The Syrian opposition had earlier said it had agreed to the "possibility" of a temporary truce, provided there were guarantees Damascus's allies would cease fire, sieges were lifted and aid deliveries were allowed country-wide.

"We have reached a provisional agreement in principle on the terms of a cessation of hostilities that could begin in the coming days," Kerry told a news conference in Amman with Jordanian Foreign Minister Nasser Judeh.

"The modalities for a cessation of hostilities are now being completed. In fact, we are closer to a ceasefire today than we have been," said Kerry, who was also to meet King Abdullah.

He declined to go into detail about the unresolved issues, saying the two sides were "filling out the details" of the agreement. And he indicated issues remained to be resolved and he did not expect any immediate change on the ground.