US President George W Bush has rejected criticism over the Guantanamo Bay camp raised by German Chancellor Angela Merkel during talks in Washington.
Angela Merkel and George Bush showed unity on some issues
President Bush said it was a necessary part of protecting the American people.
But the two leaders presented a united front over Iran resuming its nuclear programme, and commentators said they appeared to have got on well.
It is her first official US visit since her election which, Mr Bush joked, much like his own, was not a landslide win.
The two leaders discussed a range of subjects - from the Balkans and the Middle East to the Iraq war - which had strained relations between the US and Germany in recent years.
"We openly addressed that there sometimes have been differences of opinion, and I mentioned Guantanamo in this respect," Ms Merkel told the press conference afterwards.
Before leaving for the US, she had said that facilities such as Guantanamo should not exist in the long term.
But Ms Merkel said on Friday that she had been encouraged by talks with the US president and there was much more to the US-German relationship than their differing opinions on how to respond to the threat of terrorism.
She said it was going to be "essential for us not to only talk at governmental level... but our societies need to be engaged".
The BBC's Jonathan Beale, in Washington, said that after more than three hours of discussions, Ms Merkel had clearly developed a far better working relationship with President Bush than her predecessor Gerhard Schroeder ever did.
He said the president made no mention of the military option in terms of confronting Iran; instead, he stressed the need to resolve the issue through diplomacy, promising to work together with his allies.
President Bush said that referring Iran to the United Nations Security Council was part of a diplomatic process that was vital to prevent Iran arming itself with nuclear weapons.
Ms Merkel said that as many countries as possible should be persuaded to ally themselves with the US and Germany and not be intimidated by Iran.
Referring to Ms Merkel's Eastern European background, Mr Bush said it was "uplifting" to have spoken to someone who had lived through tyranny and understood the need for freedom.
On Monday, Ms Merkel is due to meet Russian President Vladimir Putin in Moscow, where Iran is likely to be on the agenda again.