Amman: US Secretary of State John Kerry urged Saturday that a ceasefire be agreed as soon as possible in Syria, during a phone conversation with Russian Foreign Minister Sergei Lavrov.
"The Secretary expressed his hope that a full cessation of hostilities could be achieved in the shortest timeframe possible," State Department spokesman John Kirby said in a statement.
Kerry, who arrived in the Jordanian capital Amman on Saturday night from London ahead of meeting King Abdullah II Sunday, again expressed his concern to Lavrov about Russian air strikes in Syria in support of President Bashar al-Assad's regime.
"Secretary Kerry also restated his deep concern over the indiscriminate nature of continued bombing by Russian military aircraft and the lives being lost as a result," Kirby said.
"The United States continues to call for all sides to abide by international obligations to avoid civilian casualties, and that responsibility lies first and foremost with the Assad regime and its supporters," he added.
The two ministers discussed progress made by two UN task forces meeting in Geneva this week, one on humanitarian aid to besieged Syrian towns and the other on a "cessation in hostilities" that had been set to come into force on Friday, Kirby said.
On Saturday in London, Kerry said in a statement that a lot of work remained to be done before reaching a truce in Syria.
Russia meanwhile promised to continue to help Damascus to fight "terrorist" groups in Syria, while a key Syrian opposition group said it would support a truce only if regime supporters halted their fire.
Kerry and Lavrov are the main architects of the Munich agreement on February 11 and 12 according to which 17 countries and three organisations agreed on a proposed ceasefire for Friday.
The European Union, which is part of the Munich grouping, separately announced that Kerry and the bloc's foreign policy chief Federica Mogherini had spoken by phone Friday and Saturday about the crisis in Syria.
"They discussed the ongoing diplomatic efforts to reach a cessation of the hostilities and the positive progress of the task force for the humanitarian assistance, in which the European Union plays a key role, that has already managed to deliver aid to the population in parts of Syria," it said in a statement.
More than 260,000 people have been killed in the nearly five-year conflict, and half the country's population has been displaced.