President Obama's scheduled visit to a former Nazi concentration camp is being done for "political reasons," the president's great-uncle -- who helped liberate that camp -- said in a recent interview. 

Obama plans to visit Germany's Buchenwald site as part of his multi-country tour, which begins this week. 

Charles Payne, Obama's great-uncle who helped liberate a sub-camp of Buchenwald during World War II, spoke frankly about the visit in an interview with Germany's Der Spiegel magazine. 

Asked if Obama would be traveling in his footsteps, Payne said: "I don't buy that. ... This is a trip that he chose, not because of me I'm sure, but for political reasons." 

He said Obama also might be trying to improve his "standing" with Chancellor Angela Merkel, since "she gave him a hard time during his campaign and also afterwards." 

Payne attracted some attention during the campaign last year when Obama mistakenly claimed he helped liberate Auschwitz -- which was actually liberated by Soviet forces. Obama's campaign corrected the mistake after Republicans seized on the error. 

In his interview with Der Spiegel, Payne said Obama's parents might have incorrectly told him the story of his great-uncle's involvement in the liberation of Buchenwald, leading to the misunderstanding on the campaign trail. Payne said he never spoke to Obama about that experience beforehand. 

"I was quite surprised when the whole thing came up and Barack talked about my war experiences in Nazi Germany. We had never talked about that before," Payne said. "Of course it came out immediately that he was wrong since there are enough people in America who know that Auschwitz is in the East and that the camp was liberated by the Red Army." 

He said Obama called him after the flap last year for more details about the camp's liberation. 

As for Obama's upcoming visit, Payne said he'd nevertheless be happy to join his great-nephew. 

"If he invites me on Air Force One, I'll be there," he said. 

He said their relationship is "warm and friendly," though he's not part of Obama's "inner circle." 

"He doesn't call me up and ask what I have to say about world policy or anything. And I never offer my opinions on any of this," Payne said. 

Obama is visiting Egypt and Saudi Arabia, as well as France and Germany. 

Click here to read the interview with Obama's great-uncle in Der Spiegel.