Although the US had sent a delegation to eight previous rounds of talks in Astana, it did not send observers to the latest negotiations.
A delegation of 24 representatives of the Syrian armed opposition has arrived in the Kazakh capital for the ninth round of talks on the Syrian crisis settlement, the Kazakh Foreign Ministry's press service said Tuesday.
Monday's talks are the first time the three guarantors have met since Iran launched rockets into the Israeli-occupied Golan Heights last week, prompting the fiercest Israeli attack on Syria since the start of the war.
"We regret this and believe the path to political settlement can only be found at the negotiating table, not in efforts and scenarios worked out behind the back of the Syrian government and the global community", he said, without elaborating.
"The Astana process is stuck right now", General Netkachev told the newspaper, "because Damascus and Moscow, with the participation of Turkey and Iran, control only about 60% of Syria's territory", reported TASS.
It is also the first meeting of the three sides since US President Donald Trump announced Washington's withdrawal from the Iran nuclear deal earlier this month in a move further complicating the regional picture.
UN Special Envoy for Syria Staffan de Mistura is expected to attend the meeting in the afternoon; Jordan would be observing the talks.
It is also the first such meeting since USA president Donald Trump announced his decision to withdraw from the Iran nuclear agreement.
Zhainaqov added that the United States was not taking part in the talks.