The CDU will hold a one-day congress under special coronavirus precautions on December 4th in Stuttgart, party general secretary Paul Ziemiak told a press conference.
The race to succeed Merkel was thrown wide open earlier this year when her protegee Annegret Kramp-Karrenbauer announced she would step down as party leader.
A meeting planned for April to elect a new leader was postponed due to Covid-19.
Back then, the three main CDU hopefuls for Merkel's job were state premier of North Rhine-Westphalia Armin Laschet, corporate lawyer Friedrich Merz and foreign affairs expert Norbert Roettgen.
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But former favourite Laschet has stumbled in managing the coronavirus response in his state, which has seen high case numbers including a huge outbreak at a meat processing plant.
Merz and Röttgen have meanwhile lost visibility in the media spotlight as Germany grapples with the pandemic.
The chief of the CDU traditionally leads it and its smaller Bavarian sister party CSU to the polls. He or she therefore has a claim on the chancellor job should the conservative bloc win the election.
But this time, speculation is running high that CSU leader Markus Söder could seek the coveted chancellor-candidate post of the conservative bloc.
Söder himself has repeatedly stressed that his place is in Bavaria.
But his tough attitude on halting virus transmission has won him plaudits, and he has as a result topped recent surveys on who Germans would like to see as their next leader.
The CDU has not ruled out fielding Söder as the chancellor candidate.
Germany's centre-left Social Democrats, the CDU's junior coalition partner, have nominated Finance Minister Olaf Scholz to lead them in the race to succeed Merkel.