Following the meeting, Mr Schauble said, according to German media "this shows that the US government is interested in good relations with Germany".

Repeating sentiment expressed by Mrs Merkel during a recent meeting with French government officials, Mr Schauble underlined the importance of the relationship between Berlin and Washington.

"German foreign policy has to find its way back to a traditional balance between good relations with the US and France", he said.

This was also a pointed reference to current chancellor Gerhard Schroder, who managed to infuriate the US when during an election campaign he referred to American plans to invade Iraq as an "adventure".

Mr Schroder then formed a very public triangle of opposition to the war with the leaders of France and Russia, further souring relations with Washington, which are still not back on a completely even keel.

According to Mr Schauble, the current German government went "flatly against its own interests".

Iraq and Turkey

But despite the goodwill displayed by both sides, it is unlikely to result in German troops being put into Iraq.

Mindful of continued strong German public opposition to the Iraq war, Mrs Merkel has underlined that while she supported the war, a CDU government would not change the no-troops policy, a point reiterated by Mr Schauble on Thursday.

Another point of difference is the CDU's approach to Turkey. The Bush administration has made no secret of the fact that it would like Turkey to become a member of the EU, but Mrs Merkel's party remains staunchly opposed to full membership, preferring instead to offer a 'privileged partnership' to Ankara.

This is not the first time president Bush has had a surprise meeting with a German politician.

He had a short meeting with the leader of Hessen, Roland Koch, in 2003. This was seen as a direct snub to Mr Schroder, who at the time was visiting the then secretary of state, Colin Powell, in an effort to improve relations between Germany and the US.

Thursday's meeting is also a clear sign that Washington believes that the Christian Democrats are going to get into power following elections on 18 September.