Iran's President Hassan Rouhani says he believes there is little hope of success for the Syrian peace talks.

Rouhani's remarks come as an international conference to try and resolve Syria's civil war is starting Wednesday in the Swiss resort of Montreux.

Later this week in Geneva, Syria's warring sides will sit down for their first face-to-face meeting since the conflict erupted in 2011.

According to the presidential website, president.ir, Rouhani says hopes are slim because some of the countries attending the talks "are behind instability" in Syria.

Rouhani spoke in the wake of a diplomatic snub to Iran after the U.N. withdrew its invitation to Tehran to attend the talks.

Iran has been Syrian President Bashar Assad's main regional ally and a staunch supporter of his government.