Germany's Christian Democrats (CDU) on Monday approved a coalition deal with the centre-left Social Democrats (SPD), bringing conservative leader Angela Merkel a step closer to a fourth term as chancellor of Europe's biggest economy.

Only 27 of 975 delegates present at the Christian Democratic Union's party congress voted against the partnership.

The plan still needs the approval from the centre-left SPD's rank-and-file, with the result to be announced on Sunday.

German Chancellor Angela Merkel had earlier urged her party members to approve the deal.

The more formidable hurdle to ending a five-month political impasse in Europe's largest economy comes next week, however.

New cabinet

The CDU party congress follows Merkel's announcement of her picks for a new, younger cabinet intended to revive the party, which has been riven by disagreements over how to respond to the Alternative for Germany (AfD) since losing votes to the far right party in national elections in September.

"We want to make our contribution to forming a stable federal government that is capable of acting," Merkel said before the vote.

"The fact we're voting on a coalition treaty today five months after the election shows that we're dealing with a difficult situation that we've never faced before," Merkel added.

She reassured delegates that the new German government would not take out any new debt, avoid tax increases, seek to renew the European Union, ensure fast internet is available everywhere in Germany by 2025, boost research spending, create 8,000 nursing jobs and take a "zero tolerance" policy on security.

Merkel said conservatives secured wins in coalition talks with the SPD, including preventing what she called the "aberration" of a single health system that the SPD had demanded to replace the current dual public-private system.

Merkel's authority waning

Merkel disappointed many conservatives by agreeing to give the SPD the powerful finance ministry in a new government. She said it was a "painful" loss but added that it was right not to let negotiations fail due to portfolios rather than substance.

She also underscored the importance of the economy ministry – which the CDU will retake after years in SPD hands.

The conference will also vote on the appointment as CDU general secretary of her close ally Annegret Kramp-Karrenbauer, widely seen as her preferred successor. Dubbed "mini-Merkel" by some media, the Saarland state premier, 55, shares some but not all of Merkel's views.

Her Catholic, western German background contrasts with Merkel's Protestant, eastern roots. While socially conservative and known for opposing gay marriage, Kramp-Karrenbauer is a strong supporter of the minimum wage and workers' rights.

After 12 years as chancellor and almost 18 years in charge of her party, Merkel's authority is waning and on Sunday, she responded to growing calls for new blood at the top of the CDU.

Merkel's efforts to forge a coalition with two other smaller parties collapsed in November. That forced her to woo the SPD, which had been a coalition partner in her 2013-2017 government but was reluctant to repeat the experience after seeing its own support fall to its lowest since World War Two.

Possible new election

If SPD members vote "no" in their ballot, the most likely outcome is a new election or possibly a minority government.

Experts say a snap election could result in further gains for the anti-immigration AfD, which entered parliament for the first time in September.

Some analysts say the prospect of a new election will spur SPD members into voting "yes", to prevent a further deterioration in support for the Social Democrats.

A Forsa poll on Monday showed the SPD up two points from a week ago, at 18 percent, while Merkel's conservatives edged up one point to 35 percent. The AfD remained the third-strongest party with 13 percent.

Forsa researcher Manfred Guellner said the grumbling in both camps had waned since Merkel proposed Kramp-Karrenbauer for CDU general secretary and former SPD leader Martin Schulz decided against joining a Merkel-led cabinet as foreign minister.