BEIRUT (AP) — Syria’s main Western-backed opposition group said Monday that Iran must commit publicly by 7 p.m. GMT to withdraw its “troops and militias” from Syria and abide by a 2012 transitional roadmap, or else the U.N. should withdraw its invitation for Tehran to take part in a peace conference.

The Syrian National Coalition said if those conditions are not met by the deadline, then it will not attend the so-called Geneva 2 conference that is scheduled to begin Wednesday. The U.N. issued a last-minute invitation late Sunday to Iran, a close ally of Syrian President Bashar Assad, prompting the Coalition to threaten to sit out the peace talks and throwing the entire Geneva conference into doubt.