Russia, a steadfast supporter of Syrian President Bashar al-Assad, is set to co-host the summit with regime ally Iran and rebel backer Turkey with the aim of setting up a new constitution for post-war Syria.
Organisers had said earlier that the peace talks were planned for January 29 and 30, but Lavrentyev said that the participants would arrive on January 29 and "the forum itself will take place on January 30".
"I consider the meeting went well. We managed to agree on lists of participants of the forum," Lavrentyev said.
He said invitations would be sent within a few days, quoted by RIA Novosti news agency.
More From This Section
Russian Foreign Minister Sergei Lavrov said at a press conference in New York on Friday that Moscow had invited around 1,500 representatives of the Syrian people "including sheikhs, tribal leaders and representatives of civil society".
The talks will come after the latest round of UN- sponsored negotiations in Geneva ended in failure in December.
The United Nations itself will host a new round of peace talks on Syria next week in Vienna.
The war has displaced millions of people and is estimated to have claimed the lives of at least 340,000 people since 2011.
Moscow said it hopes the UN will send its special envoy on Syria, Staffan de Mistura, to the Sochi forum.
He said that the United States was also expected to attend as an observer.
The January talks were announced during negotiations in Kazakhstan in December sponsored by powerbrokers Russia, Turkey and Iran. A joint statement said the congress would include "all segments of Syrian society".