The Syrian armed opposition said on Wednesday it had suspended its participation in peace talks being held in Astana, the capital of Kazakhstan, and demanded an end to government bombing of areas under its control.

Axar.az reports citing Reuters.

A source close to the talks told Reuters that the armed opposition delegation had so far not left the building where the talks were being held however, while a senior official from Kazakhstan's Foreign Ministry told reporters he expected the Syrian armed opposition to return to the talks on Thursday.

"The delegation has suspended its participation after presenting a memorandum for a total commitment to stopping (government) bombardments," Ahmad Ramadan, a spokesman for the opposition Syrian National Coalition (SNC), said.

He gave no further comment.

In a phone call on Tuesday, U.S. President Donald Trump and Russian President Vladimir Putin moved to ease the tension from U.S. air strikes in April against Russian ally Syria, expressing a desire for a Syrian ceasefire and safe zones for the civil war's refugees.

With a ceasefire ever elusive in Syria, the White House said Washington would send a representative to the ceasefire talks in Astana on Wednesday and Thursday. The State Department said acting Assistant Secretary for Near Eastern Affairs Stuart Jones would be attending as an observer.