Iranian Foreign Minister Mohammed Javad Zarif spoke by phone with UN-Arab League envoy Lakhdar Brahimi to discuss peacekeeping efforts in Syria, even as Brahimi said the United States was blocking Iran’s participation at the Syrian peace conference planned for next month.

Zarif and Brahimi discussed the upcoming Geneva II conference scheduled for January 22, AFP reported Saturday, citing an Iranian Foreign Ministry statement.

During the phone call, Zarif reportedly “insisted on a political solution” to the Syrian crisis.

On Friday, Brahimi said about 30 nations, including Saudi Arabia, would be invited to a day of speechmaking planned for Jan. 22 in the city of Montreux, and Iran’s participation was the only sticking point, but was still a possibility. The Syrian opposition also has opposed Iran’s involvement.

“Our partners in the United States are still not convinced that Iran’s participation would be the right thing to do,” Brahimi told a news conference. “We have agreed that we will be talking a little bit more to see if we can come to an agreement on this question.”

His comments came after a day of meetings with the five permanent members of the UN Security Council — Britain, China, France, Russia and the US — and Syrian neighbors Turkey, Jordan, Lebanon and Iraq.

Along with those nations, other invitees include Algeria, Brazil, Egypt, Kuwait, Oman, Qatar and the United Arab Emirates. The actual negotiations between Syrian President Bashar Assad’s government and opposition representatives begin on Jan. 24 at the UN’s European headquarters in Geneva.

Disputes over who should represent the Syrian opposition and government, and whether Iran, Saudi Arabia and other regional powers should be at the table, have blocked previous attempts to bring Syria’s warring sides for peace talks.