The foreign ministers of Iran, Russia and Turkey are set to meet in Kazakhstan next week as the three countries attempt to move forward with a plan to end nearly seven years of war in Syria.
Kazakhstan's foreign ministry said Tuesday that the top diplomats of regime allies Moscow and Tehran and rebel-backer Turkey would hold a March 16 meeting in the capital Astana "without observers or Syrian sides."
The statement also said that the United Nations Syria envoy Staffan de Mistura would be invited to the meeting.
The announcement comes as Syrian regime forces intensify bombardment of the rebel-held enclave of Eastern Ghouta, just outside Damascus.
The siege has been so intense that it even caused a UN aid convoy to cut short its mission to supply the besieged area at the beginning of the week.
Eastern Ghouta is one of four "de-escalation" zones that were devised in order to keep rebel and regime forces at arm's length as part of a plan thrashed out in Astana last year.
The United States on Monday accused the Syrian regime and its ally Russia of using "indiscriminate force" in the area in a strongly critical statement.
Talks on Syria in Astana, which have usually involved regime and opposition delegations, as well as the three guarantors, began in January 2017.
They run parallel to UN-led negotiations in Geneva and were credited with bringing about a reduction in hostilities between government and rebel forces after the agreement on the safe zones was reached.
But the government's bombardment in Eastern Ghouta that started on February 18 and killed nearly 800 in the space of 10 days, according to Medecins Sans Frontieres, appears to have reduced hopes of any peace settlement in the near future.
Assad's forces have seized over a quarter of the enclave on Damascus's eastern edges after two weeks of devastating bombardment, according to the Syrian Observatory for Human Rights, a Britain-based monitor.
More than 340,000 people have been killed since Syria's war started in 2011. It has since spiralled into a complex conflict involving world powers.