Secretary of State John Kerry and his Russian counterpart differed Monday over whether Iran should attend a peace conference in Switzerland later this month. During a news conference with Kerry and a top U.N. official, Russian Foreign Minister Sergei Lavrov repeated his country's call for Iran -- a key backer of Syrian President Bashar Assad's regime -- to be allowed to attend the Syria peace talks in Switzerland, known as Geneva II, on Jan. 22, the Wall Street Journal reported. Lavrov cited Iran's influence in the region and called U.S. opposition to Iranian presence at the Geneva talks "ideological." "Iran's participation or non-participation isn't a question of ideology. It is a question of common sense," said Kerry. He said Iran doesn't meet U.S. criteria to attend the conference. On Sunday, Iran said on its official television network that its foreign minister, Mohammad Javad Zarif, would go to Damascus, Syria's capital, within the next few days, MENA reported. "If we receive an invitation without any preconditions, we will participate in the ... peace conference, but we won't act in order to receive an invitation," Zarif said in Beirut, Lebanon. Tehran would be welcomed to the talks only if it accepted negotiating terms outlined in a previous round of negotiations, including creating a transitional government without Assad and his loyalists, Kerry said. Following a Friends of Syria meeting Sunday, Kerry expressed confidence that Syrian opposition leaders would attend the Geneva talks, MENA said. Kerry met with National Coalition leader Ahmad Jarba, whose organization includes the main opposition movement in exile. "I am confident that he and others will be in Geneva. I am counting on both parties to come together," Kerry said. The Friends of Syria is a group of mainly Western and Gulf countries opposed to Assad, who has waged a civil war with rebel forces for more than two years. In a statement, the 11-nation Friends of Syria group said that once a transitional government was in place, "Assad and his close associates with blood on their hands will have no role in Syria." The opposition has been reluctant to attend the Geneva talks without a commitment that Assad step aside, or at least stop using heavy weapons and open humanitarian corridors, Radio France Internationale reported.