Iran on Monday brushed aside a US offer of a sideline role in upcoming peace talks on Syria, saying Tehran would only accept offers that respect its “honour”.

“Iran has always announced its readiness to participate without preconditions” in talks on Syria scheduled for January 22, foreign ministry spokeswoman Marzieh Afkham told the official IRNA news agency.

“(But) Tehran will only accept offers that preserve the honour of the Islamic republic,” she said without elaborating.

Afkham made the remarks when asked about a suggestion by US Secretary of State John Kerry that Iran, Syria’s main regional ally, may be able to play a role at the US-Russia initiated talks.

The United Nations said invitations to the conference dubbed Geneva 2 were being sent out Monday, but Iran was not on the list of countries invited.

Kerry and his Russian counterpart Sergei Lavrov will meet on January 13 in a bid to decide whether Iran should take also part.

Washington has long opposed Iranian participation in the talks without it signing up to a June 2012 accord calling for a transitional government to replace the regime of President Bashar al-Assad.

But Kerry on Sunday opened the door to possible involvement by Tehran in the conference.

“Could they contribute from the sidelines? Are there ways, conceivably, to weigh in? Can their mission that is already in Geneva be there in order to help the process? It may be that there are ways that can happen,” Kerry said.

“We’re happy to have Iran be helpful.”

Tehran is accused of providing military and financial support to Damascus, despite repeatedly maintaining that it has no official military presence in Syria and that its backing takes the form of humanitarian aid.