BERLIN — German Chancellor Friedrich Merz is facing rising opposition — but this time it’s from within his own conservative ranks.

A group of 18 young lawmakers in Merz’s conservative bloc are threatening to stop a pension reform bill put forth by the chancellor’s coalition government, arguing the benefits pledged in the agreement aren’t sustainable and “cannot be justified to the younger generation.”

The revolt has turned into a test of Merz’s authority and the durability of his relatively weak government — a coalition between his conservative bloc and the center-left Social Democratic Party (SPD). Merz’s coalition only has a 12-seat majority in parliament — one of the narrowest in postwar German history — making his government vulnerable to even modest defections within the ranks.

During a conference over the weekend, Merz pushed back against criticism from young conservatives that planned pension benefits are too generous.

“Does anyone seriously believe that we can win a race to the bottom on who can offer the lowest pension levels?” Merz said. “You can’t be serious!”

Merz faced a series of harsh questions from attendees, many of whom felt the chancellor was not taking their arguments sufficiently seriously.

“Can you personally reconcile this with your credibility?” asked Laurenz Kiefer, a member of the young conservatives from Munich.

Coalition lawmakers had initially expected to pass the pension reform package in early December as part of a series of bills Merz has attempted to push through to show his government can undertake the key structural reforms Germany needs to boost economic competitiveness. But the timing of that vote has now been cast into doubt amid the internal fighting.

“I hope that we will have concluded this discussion by the end of the year so that we can enter 2026 with a genuine willingness to reform,” Merz said during an event in Berlin on Monday.

Merz is effectively stuck between the demands of young conservatives to reconsider the pension package and the obduracy of his SPD coalition partners, who say they’re not willing to renegotiate it.

“Let me be perfectly clear: There will be no further changes to this law,” SPD Finance Minister Lars Klingbeil said. “We will pass it in the Bundestag.”

The pension issue has become particularly thorny as Germany’s baby-boomer generation enters retirement, with millions of people leaving the workforce and far fewer entering it. Pensions are the largest single item of public expenditure in the country.

At the heart of the internal rebellion is a proposal to stabilize pension benefits after 2031. Young conservatives argue that this plan goes further than what was originally agreed by the coalition, and would mean over €115 billion in additional costs by 2040.

The internecine dispute has led some in Merz’s coalition — including his own family minister, Karin Prien — to propose postponing the pension reform vote to avoid the kind of embarrassment and open discord that could potentially lead to the coalition’s unravelling.

“It is important that fair solutions for the broad majority are found in parliament,” Prien told German newspaper Handelsblatt.