Russian Foreign Minister Sergey Lavrov and his US counterpart John Kerry met in Switzerland Wednesday to prepare for talks aimed at ending the war raging inside Syria, but failed to agree on the invitation list.

However, Lavrov said that the talks between the Syrian government and opposition groups would begin next Monday at Geneva as scheduled.

“We have provided our proposal, the US did the same, and now the members of the Syria opposition groups also provided their proposal” regarding the invitation list, Lavrov told reporters.

He added that it was now up to UN Syria envoy Staffan de Mistura to come up with a solution.

Al Jazeera reported that Lavrov said armed groups Jaish al-Islam and Ahrar al-Sham are not acceptable parties to the talks, calling them “terrorist organizations.” The US thinks the groups should be invited.

Jaish al-Islam and Ahrar al-Sham are both coalitions of multiple Islamist and Salafist units involved in the Syrian Civil War.

Lavrov said neither he nor Kerry had thought about postponing the talks.

“The political process will begin, we hope, as soon as possible, at the end of January,” he said. “We don’t know the actual date yet, but we are going to go forward and support the recommendations, particularly the ones made by Mr Staffan de Mistura, UN special envoy for Syria.”

“The UN Security Council is obliged to make sure that this meeting of all the Syrian actors and players takes place soon and we hope very much that it will be in this month.”

In the meeting Wednesday, Kerry called on Russia to use its influence with Syrian strongman Bashar al-Assad “to ensure immediate, unimpeded and sustained humanitarian access to all Syrians in need,” Kerry’s spokesman John Kirby said. Kerry specifically pointed at besieged communities like Madaya, where people have reportedly died of starvation.

Lavrov said the pair “confirmed the need to resolve the humanitarian problem in Syria.”