German Social Democratic (SPD) leaders appealed to party members Friday to swallow their doubts and endorse an overnight deal to renew a "grand coalition" with Chancellor Angela Merkel's conservatives for another four years.

The deal eased months of uncertainty that has undermined Germany's role as the European Union's pivotal power, as the bloc confronts such major challenges as Brexit, euro-zone reform and immigration, and questions about Merkel's future.

"The world will not wait for us," a weary-looking Merkel said Friday morning after 25 hours of talks, which yielded a deal opening the way to formal negotiations on the details.

But some in the wary SPD rank and file said the deal lacked sufficient concessions to the center-left party, which after four years of a sometimes awkward coalition with Merkel suffered its worst election results since 1933 last September.

Christian Democratic lawmakers greeted their leader with a round of applause when she outlined the arrangement, which pledged closer cooperation with France to strengthen the euro zone and a crackdown on arms sales to countries in conflict zones.

But SPD leaders will have a harder time convincing members that they should approve the pact at a Jan. 21 party congress and again in a postal vote at the end of formal coalition negotiations.

"The SPD got its way in many areas," senior SPD lawmaker ­Hubertus Heil told public broadcaster RBB in what is likely to be the first of many such entreaties to rank-and-file members in the coming week.

SPD Chairman Martin Schulz was addressing those members when, standing alongside Merkel, he told reporters that the outline deal would preserve and strengthen Germany's welfare state for future generations.

"From the kindergarten to the school, to the university and the workplace and then on into old age and care homes, we want to strengthen respect, opportunity and solidarity, and bring these systems up to date," he said.

The parties agreed to spend more on the E.U. — a long way short of Schulz's ambition to create a "United States of Europe" by 2025. The SPD's plan to create parity between private and public health care was also missing from the deal.

Pledges to spend more in poorer regions and allow up to 1,000 family members each month to join refugees already living in Germany also seemed designed to placate SPD members distrustful of governing with Merkel again.