The ruling United Russia party will meet in late September to approve its election program and finalize the list of candidates for the December parliamentary election.
The congress was originally planned for September 3-4 but Russian Prime Minister and party leader Vladimir Putin on Tuesday backed the proposal to push it back three weeks to September 23-24.
About 4,000 delegates are expected to attend, senior party member Sergei Neverov said.
The list of candidates will be based on the results of the primaries that started on July 21 and will run through August 25.
In accordance with party rules, Putin may submit or strike candidates off the list at his own discretion.
United Russia hopes that the list will be headed by the party leader who may announce his decision at the congress.