US Secretary of State John Kerry is travelling to Geneva in a show of support for the ceasefire between the Syrian Government and rebel forces.
Aleppo excluded from pause in fighting declared by Syria's military
US sees stopping bloodshed in Aleppo as a top priority
John Kerry to meet with counterparts from Jordan and Saudi Arabia in bid to save ceasefire
Mr Kerry will meet with the foreign ministers of Jordan and Saudi Arabia and UN envoy for Syria Staffan de Mistura, the State Department said in a statement.
The trip comes with a US and Russian-backed ceasefire under threat as air strikes and rocket attacks continue in the northern Syrian city of Aleppo.
The latest violence there contributed to the break up of peace talks in Geneva, which the main opposition walked out of last week.
Nearly 30 air strikes hit rebel-held areas of Aleppo on Saturday as a temporary "calm" declared by Syria's military took effect around Damascus and in the north-west.
The Syrian army announced a "regime of calm", or lull in fighting, late on Friday (local time), which Damascus said was designed to salvage the wider ceasefire.
But a number of rebel groups appeared to reject the "regime of calm".
"We won't accept any kind of ... regional ceasefires," said a statement from a number of groups including the hardline Islamist Jaysh al-Islam, which controls areas east of Damascus.
It said the main armed opposition as a whole reserved the right to respond to attacks on rebel factions in any part of the country, and criticised the United States for not doing enough to stop government bombardments.
The lull in fighting around the capital and parts of north-west coastal province Latakia, announced by the army, appeared to hold through most of Saturday but the bombing continued in Aleppo which was excluded from the plan.
Anas Al Abde, president of the Turkey-based opposition Syrian National Coalition, accused the government of violating the February truce "daily".
The opposition was ready to reinstate the wider truce, but reserved the right to respond with force to attacks, he said.
All sides have accused each other of truce violations.
Aleppo, Syria's largest city before the war, has been divided for years between rebel and Government-held zones.
Of the 250 casualties since April 22, 140 were killed in bombardments by government-aligned forces and 96 by rebel shelling.
Forty children were among the dead, according to a tally by the British-based Syrian Observatory for Human Rights.http://www.abc.net.au/news/2016-05-01/syria-ceasefire-john-kerry-head-to-geneva-to-support-truce/7373662