Why wasn’t Iran invited to participate in Geneva-2?

Ahead of the conference, the Foreign Minister of Russia Sergey Lavrov spoke about why Iran wasn't invited to participate in Geneva-2.

Secretary General of the UN Ban ki-Moon canceled his own invitation of Iran to the cconference. The official reason for cancelation of the Iranians’ invitation is their rejection of the final protocol of Geneva-1, which requires forming of a transactional government in Syria. The conference is to take place in Switzerland on January 22nd.