Staffan de Mistura said disagreements remain over a "few names" of those who would be on that committee. He said "agreement, particularly on the side of the government" of President Bashar Assad was needed.
The envoy has been trying to convene a meeting of the "constitutional committee" before year-end, and his efforts have kept him in his post later than he had expected. He told reporters that his Dec. 20 briefing to the U.N. Security Council could be his last.
De Mistura has previously said that Assad's government has objected to 50 members of the committee representing civil society, experts, independents, tribal leaders and women that he was authorized to put together at a Russian-hosted Syrian peace conference in Sochi earlier this year. Russia is a crucial backer of Assad.
At his Geneva office on Friday, de Mistura hosted China's special envoy for Syria, Xie Xiaoyan, in hopes of enlisting Beijing's support. Under the Sochi agreement, the committee is to comprise 150 members. There is already agreement on the 50-member delegation from the government and the 50-member delegation from the opposition.
"What is missing is (a) few names, just (a) few names to be agreed upon on the constitutional committee," de Mistura said. Xie said China was willing to engage in the reconstruction of Syria one day but said it would cost "hundreds of billions of dollars" that will require the effort of regional countries and world powers "including the United States."
"China will work with the international community to engage in the reconstruction work," he said. "We hope that the conditions will be appropriate meaning that security is guaranteed."