BERLIN (Reuters) - Bavarian state premier Horst Seehofer on Sunday defended his planned visit to Russian President Vladimir Putin in Moscow against warnings it could undermine German Chancellor Angela Merkel’s refugee policy.

Bavarian Prime Minister and head of the Christian Social Union (CSU) Horst Seehofer makes a speech at the Christian Democratic Union (CDU) party congress in Karlsruhe, Germany December 15, 2015. REUTERS/Kai Pfaffenbach

Seehofer, a Merkel ally who has sharply criticized her for letting in so many migrants from the Middle East and elsewhere, said the trip starting on Thursday had been agreed with the chancellor and Foreign Minister Frank-Walter Steinmeier.

German-Russian relations are tense amid concern that Moscow is trying to stoke popular discontent here over claims by a 13-year-old German-Russian girl of having been kidnapped and raped by migrants in Berlin. Prosecutors said on Friday they had proof the claim was false.

The Ukraine crisis and Syria’s civil war have also soured bilateral ties, and German media have accused Moscow of secretly cooperating with far-right anti-immigrant parties that have been gaining support in Germany and other European countries.

“We have prepared this trip very carefully ... and we are not pursuing any parallel foreign policy,” Seehofer told ZDF television, adding it was primarily motivated by the good relations - especially in trade - between his rich state and Russia.

Critics across the political spectrum were not reassured.

“Seehofer has clearly positioned himself against the chancellor in the debate on refugees - I really hope he doesn’t go on this trip,” said Roderich Kiesewetter, a foreign policy spokesman for Merkel’s conservatives in parliament.

“If Seehofer goes, he needs to warn the Russians that they need to stop the hybrid falsification of information and the undercover financing of radical right-wing networks,” he told the newspaper Welt am Sonntag.

Deputy Niels Annen from the Social Democrats, Merkel’s junior coalition partner, told the same newspaper: “Foreign policy is made in Berlin, not in Munich”, referring to the state capital of Bavaria.

Juergen Trittin, foreign policy spokesman for the opposition Greens, told Welt am Sonntag that Seehofer would meet a “kindred spirit” when he visits Putin.

“One organizes resistance among the conservatives to a humanitarian refugee policy while the other uses his propaganda network to mobilize hundreds of German-Russians to hold hostile demonstrations outside German refugee homes,” he said.

The Berlin rape case led to an unusual war of words last week when Russian Foreign Minister Sergei Lavrov accused German authorities of “sweeping problems under the rug” by covering up the rape case.

Steinmeier hit back with a sharp warning to Moscow not to exploit the case for “political propaganda” and to influence the politically sensitive immigration debate in Germany.

Bavaria, the first stop in Germany for migrants coming along the so-called Balkan route, has borne the brunt of the influx and its government calls the burden unbearable.

Seehofer’s Christian Social Union (CSU), the Bavarian sister party to Merkel’s Christian Democrats (CDU), has been among the strongest voices demanding that Merkel close the frontiers and send back migrants with no right to political asylum.

Seehofer has even threatened to file a complaint against the government’s refugee policy with Germany’s Constitutional Court. In the ZDF interview, he said Bavaria would have to decide by the end of February if it goes through with this threat.