BERLIN (Reuters) - The leader of Germany’s Social Democrats (SPD) said on Monday he wanted to renegotiate key issues agreed in a coalition blueprint with Chancellor Angela Merkel’s conservatives after his party narrowly approved the start of formal coalition talks.

Social Democratic Party (SPD) leader Martin Schulz arrives for talks at the party headquarters of the Christian Democratic Union (CDU) in Berlin, Germany, January 22, 2018. REUTERS/Hannibal Hanschke

At an SPD congress where divisions over the proposed alliance were laid bare, 56 percent of delegates voted on Sunday to start formal negotiations on the basis of the blueprint.

That was tighter than many experts had expected, with discontent among the rank-and-file widespread. The SPD leadership tried on Monday to appease critics by demanding that the conservatives make concessions on immigration and healthcare.

An RTL poll conducted on Monday indicated the party’s support had dropped a point to 17 percent, well below the 20.5 percent it won in September, itself a post-war low, and just four ahead of the far-right Alternative for Germany (AfD).

Merkel, Horst Seehofer, the leader of her Bavarian CSU allies, and SPD head Martin Schulz met on Monday to discuss the timetable of negotiations.

Schulz said that “we will talk about all the topics we addressed in the exploratory talks again”.

SPD General Secretary Lars Klingbeil told the public broadcaster ARD that the SPD wanted to add a “hardship provision” to an agreement that caps the number of family members who can join refugees already accepted in Germany at 1,000 a month.

He also hoped the conservatives would give ground on the single “citizen’s insurance” that the SPD wants to replace Germany’s dual private and public healthcare systems.

If SPD leaders fail to deliver more, the risk increases that the party’s 443,000 members might reject a final deal when they are asked to vote.

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A conservative-SPD ‘grand coalition’ has governed Europe’s economic powerhouse since 2013, and a re-run appears to be Merkel’s best chance of securing a fourth term as chancellor.

She said she looked forward to intensive talks on forming a stable government and her priorities were preserving Germany’s economic strength and ensuring social justice and security.

Investors and partner countries are worried that policymaking in Germany and Europe may become hamstrung by a political deadlock that is about to enter its fifth month.

NO CONCESSIONS?

Schulz, whose leadership was on the line on Sunday, said the vote handed him a “duty to fight for all those who voted against”.

SPD parliamentary leader Andrea Nahles said she would negotiate “until the other side squeals”.

But Volker Bouffier, a lawmaker for Merkel’s Christian Democrats (CDU), ruled out any major changes to the blueprint.

“The key issues can no longer be called into question,” he told the daily Bild.

Juergen Hardt, conservative foreign policy spokesman in parliament, told Reuters the formal negotiations could begin this week and might be concluded by mid-February.

“Changes (to the blueprint) can only be made by mutual consent, because everyone has already given up something to get to the agreement in the exploratory talks,” he said. “The cornerstones are clear.”

Both parties suffered heavy losses to the far right in September’s election and Merkel was weakened further by the collapse in November of coalition talks with the Greens and the pro-business FDP.

The blueprint envisages a review of the next government’s progress after two years to assess if changes are needed, sparking speculation that the conservatives might also be engineering an opportunity for Merkel to step down.