0530 GMT June 28 2017
"At this time there is no indication that the meeting will be postponed. The date of January 23 is set," the source told AFP of the negotiations to be hosted by Russia and Turkey between the Syrian government and armed opposition groups.
Russia and Turkey last month brokered a cease-fire in the ravaged country which was backed by the opposing sides in the protracted war but was done without the involvement of the US, a negotiator in previous cease-fires.
The truce went into effect on December 30 and has brought calm to much of Syria though fighting continued in some places like the outskirts of Damascus amid disagreements over locations of terror groups which are not part of the cease-fire.
The diplomatic source said Wednesday that current preparations for the peace talks involve compiling a list of participants.
Some groups have already expressed concern over whether the meeting will be fully representative, with the Syrian Kurds, Western allies in the Syrian war but despised by Turkey, on Tuesday saying they were not invited.