Germany's Social Democrats (SPD) said Friday they were ready to hold talks that may help caretaker Chancellor Angela Merkel resolve a deep political crisis without calling new elections.

"The SPD is of the firm conviction that there must be talks," its general secretary Hubertus Heil said after an eight-hour, late-night meeting headed by SPD leader Martin Schulz.

"The SPD will not be closed to those talks."

Merkel's conservative bloc won a September 24 vote, but without a clear majority, in part due to the rise of the far-right, anti-immigration AfD which took millions of votes from mainstream parties.

Veteran leader Merkel has since failed to find coalition partners to govern the EU's largest economy for her fourth term.

The centre-left SPD -- Merkel's former junior coalition allies -- vowed to go into opposition immediately after the election in which they scored a dismal result.

However, Merkel's talks with two other parties, the left-leaning Greens and pro-business FDP, collapsed early this week when the FDP unilaterally pulled out.

Merkel now faces few options short of new elections: asking the SPD to enter a new "grand coalition", or running a minority government, possibly with the Greens, and asking the SPD to cooperate on an issue-by-issue basis.

- 'Credibility problem' -

Schulz has repeatedly rejected governing in Merkel's shadow, but he is facing mounting pressure within his party ranks to rethink to stop Germany from sinking into months of paralysis.

"The SPD cannot behave like a child sulking in the corner," said SPD justice minister, Heiko Maas.

President Frank-Walter Steinmeier -- who holds the power to call snap polls and who is himself a senior Social Democrat -- also turned up the heat, saying that this "is the moment when all participants need to reconsider their attitude".

Steinmeier met SPD leader Schulz on Thursday as part of a series of talks he is holding with all parties.

The SPD's deputy chair Manuela Schwesig stressed Friday that the SPD was "not automatically headed for a grand coalition".

She said the conservatives, Greens and FDP had left "a pile of broken glass" two months after the election, and that "we can't be asked to pick up all the shards within two days".

"The two options now are for the SPD to join a grand coalition or to tolerate a conservative minority government," said political scientist Oskar Niedermayer.

The SPD's dilemma was that, after Schulz categorically ruled out working with Merkel, any change of position could spell "a major credibility problem" for the party, Niedermayer, of Berlin's Free University, told news channel NTV.

source: AFP