The negotiations are intended to bring together for the first time representatives of President Bashar Assad's government and members of the Western-backed opposition that is trying to overthrow him. The conference aims to broker a political resolution to a conflict that has killed more than 130,000 people and touched off the worst humanitarian crisis in decades.
In its statement, the Coalition called on Iran to make a "clear public commitment" to withdraw all of its troops and militias from Syria, commit to all the terms of a 2012 roadmap for Syria agreed to by world powers that includes a transitional government with full executive powers.
"In case of failure to obtain the pledge, we ask Secretary-General Ban Ki-Moon to withdraw the invitation to Iran. Otherwise, the Syrian Coalition will not be able to attend the Geneva 2 conference," the Coalition said.
Iran has supplied Assad's government with advisers, money and materiel since the 2011 Syrian uprising began. The Islamic Republic's allies, most notably the Lebanese Shiite militant Hezbollah group, have also gone to Syria to help bolster Assad's forces.
The U.S., which along with its European allies is a key supporter of the opposition umbrella group, threw its weight behind the Coalition's strong stance against Iran's participation.
In Washington, senior U.S. officials said Iran has still not met the criteria to participate in an upcoming international conference on Syria and its invitation to attend should be withdrawn unless it fully and publicly endorses the aims of the meeting.
Speaking to reporters on Monday, the officials said public statements from Iran about the conference fall "well short" of what is required for Tehran's participation. They said that the United Nations must rescind the invitation unless that changes.