The Turkmen President is in Tehran for bilateral talks and also to take part in the third summit of the Gas Exporting Countries Forum.
The summit is to open on Monday with the speech of President Rouhani.
So far, the presence of presidents of Bolivia, Russia, Equatorial Guinea, Nigeria, Venezuela and Iraq has become certain. Turkmen president will also attend Monday meeting as a special guest.
Russia, Iran, Qatar, Algeria, Bolivia, Egypt, Equatorial Guinea, Libya, Nigeria, Trinidad and Tobago, Venezuela, and the United Arab Emirates, are main members of the gas exporting body. Observer countries are the Netherlands, Iraq, Oman, Peru, Azerbaijan and Norway.