Germany's Christian Democratic Union (CDU) committees are preparing the two-day party conference in Hamburg on Thursday.

Polls predict a close race for Merkel's succession to the party leadership between Annegret Kramp-Karrenbauer, who is favored by Merkel, and Friedrich Merz who finds many supporters in the CDU conservative members.

Former finance minister Wolfgang Schaeuble was the most prominent CDU member to speak out in favor of Merz as the new CDU leader and justified his decision not only in the interest of his party but also of Germany as a whole.

"It would be best for the country if Friedrich Merz obtained a majority at the party conference," he told the Frankfurter Allgemeine Zeitung on Wednesday.

In response, economics minister Peter Altmaier criticized the public recommendation of Schaeuble for Merz and told newspaper Rheinische Post on Thursday that he himself had not publicly expressed his preference for Kramp-Karrenbauer out of respect for the delegates of the CDU party conference, adding that Kramp-Karrenbauer had the best chances to "unite the CDU and win elections".

At the Hamburg party conference on Friday, the 1,001 delegates will decide on Merkel's successor at the top of the CDU but not for the chancellorship. According to Altmaier, there was a "clear wish" both within the CDU and beyond that Merkel would not end her term as chancellor before 2021.

Ralph Brinkhaus, who leads the conservative union of CDU and CSU, also strongly opposed speculations about an early new election leading to a change in the chancellor's office.

"In the 2017 Bundestag elections, the voters gave the union and Angela Merkel as the top candidate, the mandate for government for the entire election period," Brinkhaus told the German press agency.

Among CDU members, a recent poll by infratest dimap saw Kramp-Karrenbauer ahead of her rival Merz. 48 percent want Merkel's favorite candidate to take the party lead while 35 percent of CDU members polled support Merz.

Regardless of the result of the vote during the CDU party conference, 72 percent of polled party members welcomed the competition for Merkel's succession as something positive. In October, Merkel announced not to run for party lead again and refrain from any political offices after her fourth term.