"I and many young SPD members are more disappointed by the result than anything else", Kuhnert said.
A senior conservative lawmaker on Tuesday told Germany's Social Democrats they would jeopardise a hard-fought coalition agreement if they went overboard with spending plans for Europe.
The two blocs reached a 179-page coalition agreement document in early February, detailing the main issues such as policy orientations, spending and which party will name ministers in the new government. Key positions once held by Merkel's own conservatives will be handed over to SPD leaders, and policies will begin shifting to the center-left to match.
As the chancellor candidate of the biggest party, Merkel is poised for the fourth time to be elected as the new chancellor in the March 14 plenary session of the Bundestag, or the Federal Parliament, and the new government will be formed accordingly.
But the chancellor, in power for 12 years, has had to pay a high price to coax the reluctant Social Democratic Party (SPD) back into another loveless "grand coalition".Congratulating the SPD for its "clear result", Merkel said using her CDU party's Twitter account that she was looking forward to "further cooperation for the good of our country".
Belgian Prime Minister Charles Michel expressed hope that the end of Germany's six-month political limbo would allow the European Union to step up efforts to deal with such issues as immigration, security and trade.
"We now have clarity", the acting SPD leader, Olaf Scholz, said.
But she avoided the threat of early elections or trying to form a minority government. After the second Grand Coalition between 2013 and 2017 as a junior coalition partner, the share fell to 20.5 percent in September elections.
Instead, the coalition plans to set up a special commission for the phase-out of coal with a climate-change action plan to be agreed by end-2018 which will set binding targets for 2030 for all sectors including transport, heating and agriculture to cut carbon emissions.
"If the Social Democrats continue to fall in the polls, then the point will come at some stage when they say "we must get out of the government", said Nils Diederich, professor at the Free University of Berlin.
The inclusion in the coalition deal of a clause that envisages a review of the new government's progress after two years is widely seen as giving the SPD an exit should it want one and has also fuelled a debate about the post-Merkel era.