German politicians are critical of a tentative plan by Barack Obama to speak at the Brandenburg Gate in Berlin.
Erwin Huber, the leader of one of the main governing parties, said the Democratic White House hopeful had played no part in German reunification.
Chancellor Angela Merkel earlier said it was "a bit odd" that Senator Obama should speak at the Cold War landmark.
Senator Obama is to visit Europe and the Middle East in late July.
The Brandenburg Gate is one of several locations his campaign team has inquired about as the venue for a speech.
Berlin city officials have the ultimate say over whether to grant him permission to speak at the Brandenburg Gate.
Mr Huber is the head of the Christian Social Union (CSU), the sister party to Mrs Merkel's conservative Christian Democratic Union.
Mrs Merkel said earlier in the week that she would not like to see the historical landmark used for "electioneering".
The Brandenburg Gate became a symbol of Germany's division - and later reunification - when it was cut off by the Berlin Wall that East Germany's Communist leaders built in the 1960s.
It was the backdrop for a famous speech by former US President Ronald Reagan in 1987, when he called on the Soviet Union to tear down the Berlin Wall.
President John F Kennedy also delivered a major speech in Berlin.