“This does mean that we have any trilateral project. Our three countries don’t have any unique position on the Syrian crisis,” Lavrov told reporters after talks with Zarif in Moscow.

A source in the Iranian Embassy in Moscow said the Russian, Iranian and Syrian foreign ministers would have a brief meeting to discuss the Syrian crisis later on Thursday.

Lavrov said Russia is concerned by attempts to limit the number of Syrian opposition forces at the conference and insisted that both Iran and Saudi Arabia attend the talks.

Iran’s foreign minister said Thursday that Tehran would attend the Geneva-2 peace talks on Syria next week if given an unconditional invitation. “We do not accept any preconditions on the country’s participation judging from the sense of dignity and honor of [Iran],” Zarif said.

Syria’s opposition continues to demand President Bashar Assad’s ouster as a precondition of ending a civil war in the country that has dragged on for over two years and claimed the lives of at least 130,000 people, according to UN figures.

Russia and the US, the main organizers of the conference, are still split on inviting Iran. Both Russia and Iran back the Assad regime and have rejected the use of force as a solution to the conflict.

US Secretary of State John Kerry said last week that Iran could play an informal role in the upcoming Geneva-2 talks.

The international peace conference is scheduled to take place on January 22 in the Swiss city of Montreux, on Lake Geneva. It is expected to bring together the conflicting sides in the Syrian civil war, as well as influential Middle Eastern countries, the United Nations and major world powers.

The conference is designed to be a follow-up to last summer’s international meeting in the city of Geneva that drafted a peace roadmap for Syria.