If Angela Merkel becomes the German chancellor again, nearly half of all voters would want her to quit her term early, according to a poll offering a rare sign that domestic support for Europe's most influential leader may be waning.

The YouGov survey, commissioned by Germany's dpa agency and published in yesterday's Die Welt newspaper, showed 47 percent of respondents wanted Merkel to step aside before 2021, when her fourth term would end - up from 36 percent in a poll taken at the beginning of October. By contrast, 36 percent want her to serve a full four years, compared to 44 percent three months ago.

The Social Democratic Party (SPD), which lost ground among voters after the coalition with Merkel, has been reluctant to commit to a rerun as it looks to keep a sceptical rank and file on board.

SPD Foreign Minister Sigmar Gabriel, a former leader of the party, adopted a tough tone Wednesday in top-selling daily Bild.

"If the chancellery continues to reject all the proposals for EU reform, there will be no coalition with the SPD," he told the paper, as reported by Reuters.

The SPD's current leader, Martin Schulz, has championed deeper eurozone reform, calling for a United States of Europe by 2025. Gabriel also said the conservatives needed to reform the health system to close the gap between private and state care.

An INSA poll in Bild put Merkel's conservatives up two points at 33 percent and the SPD down 0.5 percent at 20.5 percent.

The far-right Alternative for Germany (AfD) which, capitalizing on voters' fears about growing inequality and the impact on Germany of Europe's migrant crisis, entered parliament for the first time in September, was down one point at 13 percent.

Many commentators have suggested the AfD would make gains if new elections were held due to a failure on Merkel's part to form a government.

Coalition talks between Merkel's conservative bloc and the center-left Social Democrats are to start on Jan. 7, which could result in either a repeat of the last so-called grand coalition or a minority government led by Merkel. A complete failure in the talks, however, could see early elections in 2018.

Europe's most populous country and top economy has been in a political stalemate since veteran center-right leader Merkel won a Sept. 24 election without a governing majority. A repeat coalition is Merkel's best chance of securing a fourth term as chancellor after talks on forming a three-way alliance with two smaller parties broke down, leaving Europe's largest economy in an unprecedented state of uncertainty.

The conservatives and the SPD have identified 15 policy areas for exploration, including education, the welfare state and employment law, where the SPD is keen to carve out a distinctive, left-wing identity for itself after a disastrous election showing blamed in part on Merkel's dominance.

The SPD's membership, which tends to be more radical than the party leadership, will have to ratify any decision to repeat a coalition with Merkel, who has been in power for 12 years. Major hurdles remain for the SPD, which in a Jan. 21 party congress in the western city of Bonn, some 600 delegates would have to agree to the launch of formal coalition talks.