U.S. Secretary of State John Kerry said he hoped for "clarity" within 24 to 48 hours on Syrian peace talks that were supposed to have started in Geneva on Monday, and that it was better to delay a few days than to have them crumble at the start.
Kerry told reporters on a visit to Laos he agreed with the United Nations Special Envoy for Syria Staffan de Mistura that invitations for the talks should not be sent out until "you have pieces lined up."
The future of the talks was in the hands of the Syrian parties, he added.
"They have to be serious. If they are not serious, war will continue. Up to them - you can lead a horse to water; you can't make it drink," Kerry said.
"We have created a framework; the Syrians have the ability to decide the future of Syria.
"We will have to see what decision Staffan makes as to exactly how he is going to begin; but we don't want to decide and have it crumble on day one. It's worth taking a day or two, or three, or whatever.
The talks between the Syrian government and opposition had been due to start in Geneva on Monday, but a Western diplomat said on Sunday they were unlikely to begin before Wednesday.
The Syrian government has said it is ready to attend, but the opposition's High Negotiation Committee, which groups political and armed opponents of President Bashar al-Assad, has said it will not until the government halts bombardments, lifts blockades, and releases detainees - steps mentioned in a United Nations Security Council resolution last month.
Kerry said he hoped for "clarity" within 24 to 48 hours.
He rejected comments from the lead negotiator of the Syrian opposition, who said on Sunday it was coming under pressure from him to attend the talks.
"I don't know where this is coming from. Maybe it's a pressure thing or an internal political thing, but that is not the situation," he said.
"They are the negotiators; so they will decide the future. What I did tell them is that it's by mutual consent. You have a veto, so does he, so you are going to have to decide how to move forward here," Kerry said, referring to Syrian leader Bashar al-Assad.
"The position of the United States is and hasn't changed, that we are still supporting the opposition politically, financially and militarily," he added.
Kerry said another meeting of the International Syria Support Group, of countries supporting the Syria peace process, had been "tentatively" called for Feb. 11.