All sides of the Astana process on Syria have confirmed their participation in the upcoming talks, which will take place on May 14-15 in the Kazakh capital. The delegations from Russia, Turkey and Iran, as well as the Syrian government and armed opposition, will take part in the talks, the Kazakh Foreign Ministry press service said on Saturday, adding that UN special envoy for Syria Staffan de Mistura will also take part in the meeting as an observer. The US delegation's participation in the upcoming round of talks as an observer has yet to be confirmed, RIA Novosti reported, citing its source.