BERLIN: Two conservative leaders locked in battle for Angela Merkel's crown failed to reach a deal by their self-imposed deadline, pushing the chancellor's CDU-CSU alliance deeper into crisis Monday months before elections.

Armin Laschet, the chief of Merkel's CDU party, and Markus Soeder, the leader of Bavaria sister party CSU, have been in a scrum for a week over who will lead the conservatives into elections in September.

The rivals had earlier said an agreement would be found by the end of the week but party sources told AFP Sunday that a deal was still out of reach with closed-door negotiations between both men ongoing.

Soeder and Laschet flew in on Sunday night to Berlin for talks, German media reported.

As head of the Christian Democratic Union, Merkel loyalist Laschet would normally be the obvious choice for the alliance's chancellor candidate nomination.

But with support for the parties plumbing new lows amid anger over Germany's pandemic management, the more popular Soeder has put up a formidable challenge against Laschet.

Soeder, who declared his bid for the job last Sunday, had then said he would step aside "without resentment" if larger party CDU was to decide for his rival Laschet.

But even after the CDU's leadership came out a day later in support for Laschet, Soeder refused to back down. Instead, the 54-year-old cited popularity ratings as he dug in his heels.

A recent poll by public broadcaster ARD showed 44 percent of Germans in favour of Soeder as most qualified as the CDU-CSU's chancellor candidate. Laschet only had 15 percent of support.

The infighting has thrown the conservatives into disarray as Merkel is about to bow out after 16 years in power.

It has also sapped energy at a time when Germany is struggling to put down a raging third wave of the coronavirus pandemic that has already claimed almost 80,000 lives in Europe's biggest economy.