BERLIN — Chancellor Angela Merkel sought Thursday to wrap up talks on whether formal negotiations to form an ideologically disparate new German government can begin, saying success would send an important signal “at a time of great polarization.”

Germany’s Sept. 24 election left Merkel’s conservative Union bloc seeking a previously untried coalition with the pro-business Free Democrats and the traditionally left-leaning Greens. After four weeks of exploratory talks which have been rancorous at times, the parties aim to decide Thursday or early Friday whether they have enough common ground to move to the next phase.

So far, the parties have struggled to overcome longstanding differences, particularly on immigration and climate change-related issues.

A decision to open coalition negotiations, which would likely last several more weeks, would require approval by a Greens congress. Failure could lead to new elections as the center-left Social Democrats, Merkel’s partners in the outgoing government, are adamant they will go into opposition after a disastrous result in September.

“It is often said in Germany that the parties are no longer distinguishable,” Merkel said as she entered Thursday’s talks. “Anyone who has taken part in these negotiations knows that there certainly are differences — serious differences.”

She called on negotiators to bear in mind what is important for the other parties involved.

“If this succeeds — and I can say for myself that the will is there, even if it is hard work — something very important can come out of it for our country at a time of great polarization,” Merkel added. “Namely, that (parties with) very, very different positions are able to act together for the people of our country.”

One major sticking point stems from the influx of more than a million migrants to Germany in 2015 and 2016. People granted a form of protection that falls short of asylum, something that has increasingly applied to Syrians, currently aren’t allowed to bring their closest relatives to join them in Germany.

The Greens want to change that, arguing that it is essential to their integration and wouldn’t entail huge numbers of extra migrants. Merkel’s conservatives say the block must stay in place.

Another sticky issue has been demands by the Greens to end the use of coal, which currently accounts for about 40 percent of Germany’s energy mix, and of combustion engines.

More generally, there is open distrust between the parties — particularly the Greens and the Christian Social Union, the socially conservative Bavaria-only sister to Merkel’s Christian Democratic Union, which is smarting from a poor performance in September and faces a tricky state election next year.

Polls have suggested that another election would produce a parliament very similar to the current one, in which the nationalist, anti-migration and anti-establishment Alternative for Germany is the third-largest party.