ASTANA (Reuters) - Russia, Turkey and Iran have postponed a planned round of talks on Syria in Kazakhstan, which Moscow had proposed to hold on June 12-13, the Kazakh Foreign Ministry said on Thursday.

A spokesman for the ministry said it was unclear when the next round of negotiations, which have also involved the Damascus government and some rebel factions, could take place.

Mikhail Bogdanov, a Russian deputy foreign minister, said the negotiations could resume on June 20, adding the date was preliminary, according to Russian news agencies.

The meeting was postponed because the delegations were not prepared, he said without providing further details.