U.S. Secretary of State John Kerry says he will meet Russia's foreign minister next week in Laos to review a plan to solidify Syria's tattered truce and restart long-stalled negotiations on a political transition.

Kerry said Friday he would see Sergey Lavrov on the sidelines of a Southeast Asia regional security conference in Vientiane on Monday or Tuesday. He said the proposal, agreed to last week in Moscow, is "showing a modicum of promise" and that the U.S. wants to test Russia's commitment to pressing the Syrian government to halt attacks on rebels.

Kerry spoke to reporters in Vienna before leaving for Paris where he was to meet with Palestinian leader Mahmoud Abbas. That meeting, though, has been postponed until later this month because of a death in Abbas' family.