VIENTIANE, Laos — U.S. Secretary of State John Kerry on Monday dismissed Syrian government claims and opposition complaints as posturing ahead of U.N.-led peace talks that are supposed to begin this week.

Kerry, in Laos after discussing the negotiations with officials in Switzerland and Saudi Arabia last wweek, said he expected there would be clarity about when the talks would start within the next 72 hours. They had been due to start on Monday in Geneva, but have been delayed because of disagreements over which groups can represent the opposition at the table.

Since arriving in Laos on Sunday, Kerry said, he had spoken to the U.N. special envoy for Syria and the foreign ministers of Russia, Saudi Arabia, France and Turkey to try to reach consensus on how the talks will be run and a planned ceasefire would proceed.

“We’re going to have the meeting and (the talks) are going to start,” Kerry told reporters. “But what we are trying to do is to make absolutely certain that when they start everyone is clear about roles and what’s happening so you don’t go there and wind up with a question mark or a failure. You don’t want to start Day One by not being able to make progress.”

He said his conversations with colleagues were mainly about how the cease-fire and confidence-building measures, such as opening up areas for humanitarian access, would work. He declined to elaborate but said any disagreements arising in the Geneva talks would be addressed by another meeting of the 20-odd member International Syria Support Group that is tentatively scheduled for Feb. 11.