Mrs Merkel said the US talks will not solely be on terrorism
German Chancellor Angela Merkel says the US detention camp at Guantanamo Bay "should not exist", in an interview days before she meets George W Bush.
In the interview to be published on Monday, Mrs Merkel criticises the US camp in Cuba, saying "different ways" should be found to deal with prisoners.
Her visit to Washington is her first since she took office in November.
Mrs Merkel hopes to improve relations with the US, which were strained when Gerhard Schroeder opposed the Iraq war.
Mrs Merkel told the German magazine Der Spiegel: "An institution like Guantanamo can and should not exist in the longer term.
"Different ways and means must be found for dealing with these prisoners."
At a news conference on Saturday, Mrs Merkel defended her comments, but said she would not demand the immediate closure of the camp when she meets with President Bush next week.
"That's my opinion and my view and I'll say it elsewhere just as I have expressed it here," she said.
Human rights campaigners have protested over Guantanamo Bay
"My talks with leaders of other countries don't consist of my expressing demands but of exchanging views."
The chancellor told Der Spiegel she expected to speak to Mr Bush about the fight against terrorism.
"But I want to accentuate that our relationship with the US will not be reduced to talking about fighting terrorism and the Iraq war," she said.
Mrs Merkel's Social Democrat partners in the coalition government welcomed her condemnation of Guantanamo.
"The Guantanamo camp must be closed. The Guantanamo system was and still is bad," said the party's parliamentary leader Walter Kolbow.
"It was and remains in contradiction with the agreements and standards of international law."
Human rights campaigners have expressed growing concern about the treatment of inmates at Guantanamo.
The Bush administration has denied allegations of abuse at Guantanamo, insisting it does not torture prisoners.