By Madeline Chambers
BERLIN (Reuters) - Hungarian Prime Minister Viktor Orban, a fierce critic of German Chancellor Angela Merkel's open-door migrant policy, is to visit her former mentor Helmut Kohl later this month, raising eyebrows among German politicians.
Kohl, a former chancellor and the architect of Germany's reunification, will host the right-wing Orban - who has repeatedly clashed with European Union authorities - at his home in Ludwigshafen on April 19, his office confirmed.
The Hungarian government declined to comment.
Kohl is now in fragile health, having been in and out of hospital in recent years and making only rare public appearances. He is largely confined to a wheelchair.
It was unclear why Orban wanted to visit Kohl, 86, a Christian Democrat who was a towering driver of European integration during his 1982-1998 tenure as chancellor and remains a strong proponent of a united Europe.
"I have little doubt that he will make this view clear in any talks that he has," said Peter Tauber, General-Secretary of Merkel's conservative Christian Democratic Union (CDU).
While Merkel was Kohl's protégé in the 1990s, their relations soured after she called on the CDU to break with its "old warhorse" over a party funding scandal. Since then, Kohl has voiced doubt about some of Merkel's policies, including her handling of the euro zone debt crisis.
Conservative allies have brushed off any suggestion that Orban's visit might be intended as a snub to Merkel, saying Kohl is entitled to see whoever he likes. Further details of the trip are unclear but a German government source said there were no plans for Merkel to meet Orban.
Last month the Hungarian premier visited Bavarian conservative leader Horst Seehofer, who has also demanded a tougher line from Merkel on migrants, more than 1.1 million of whom have entered Germany since the start of last year.
Germany's Social Democrats (SPD) called on Kohl to try to influence Orban, a feisty nationalist whose right-wing government has been at odds with the EU on issues ranging from the economy to immigration since he took office in 2010.
"He must use the opportunity to talk bluntly with Orban about freedom of the press and of expression in Hungary and the migrant crisis," said SPD General Secretary Katarina Barley.
Orban has promised to protect Hungary from the influx of migrants into Europe and his government built a razor wire fence on the border with Serbia and Croatia. His critics describe some of his reforms as heavy-handed and authoritarian.
(Additional reporting by Andreas Rinke and Krisztina Than in Budapest; Editing by Mark Heinrich)