On Monday, in an apparent bid to reassure voters and appease Mr Merz, the German government announced that it would impose additional checks at all land borders for six months, starting next Monday.
Germany is already carrying out extra border checks on its eastern frontiers with Poland, the Czech Republic and Switzerland, while additional checks with Austria have been in place since 2015.
Monday’s announcement will extend those checks to Germany’s western borders with France, Luxembourg, the Netherlands, Belgium and Denmark.
Germany is part of the EU’s open-border Schengen zone, where additional border checks are only permitted as a last resort for member states on national security grounds.
It came as a senior member of Germany’s Green faction, which is in coalition with Mr Scholz, accused Mr Merz of using migration as a tool to “blackmail” the government.
“Friedrich Merz is behaving like a stubborn child,” said Irene Mihalic, the manager of the Greens’ parliamentary faction, referring to earlier rumours that he may not attend Tuesday’s summit. “These blackmail attempts are just ridiculous.”
Bild, the country’s leading tabloid, welcomed Monday’s border announcement, describing it as a “victory for the majority of German citizens who have long been demanding stricter asylum rules”.
It added that the announcement was a political boost for Mr Merz, who is seeking victory in next year’s national elections, because he “forced the government into the asylum confrontation two weeks ago”.