Insisting "this is serious", the leader of Chancellor Angela Merkel's Bavarian sister party stood by his demand for a refugee cap and said the conservative allies still have differences to resolve before campaigning for September's election.
Horst Seehofer, the leader of the conservative Christian Social Union (CSU), said on Wednesday a "reconciliation summit" he is due to hold with Merkel in Munich in February was still planned but that the programme was not finalised.
The CSU has long bristled at Merkel's open-door policies that allowed into Germany about 1.1 million refugees from Syria, Iraq, Afghanistan and elsewhere since mid-2015. Ignoring her objections, it insists on a limit of 200,000 refugees per year.
By saying the two parties, who form the conservative "Union" bloc, still have differences to resolve, Seehofer kept up pressure on Merkel to toughen her stance on migrants.
"We still need to discuss some things and then we will go into the election together," Seehofer said of his CSU and Merkel's Christian Democrats (CDU), speaking at the beginning of his party's annual January retreat.
"This country is polarised and divided and it must be the task of all democrats to lead their country together," he said.
The migrant issue has become more heated after an attack before Christmas in Berlin in which an asylum-seeker from Tunisia killed 12 people. After that, the CSU pushed for the Mediterranean Sea route for migrants to be closed by sending them back to Africa rather than allowing them to stay in Europe.
Merkel and Seehofer's February meeting in Munich was planned after they each stayed away from the other's party conference late last year as their conservative alliance struggles to repair the divisions over migrant policy.
Members of the CDU are concerned the divisions have not healed.
Ahead of the national election, the CSU is worried about losing votes to the far-right Alternative for Germany (AfD) party that takes a hard line against refugees.
Seehofer is also looking ahead to a regional election in Bavaria in 2018, worried about losing votes then too to the AfD, which punished Merkel's CDU in other state votes last year.
Appealing to his Bavarian base, Seehofer rejected a proposal by Merkel's interior minister for Germany's state intelligence agencies be centralised. At the moment, each of the 16 federal states has its own.