Earlier this week, Merkel said Germany would support a new round of tougher UN sanctions against Iran but she has repeatedly stressed the need for a diplomatic solution. 

Diplomatic track

Dana Perino, White House spokeswoman, said that the two leaders would discuss Iran "and the need for our countries to work together on the diplomatic track to get Iran to halt its uranium reprocessing and enrichment".

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Johndroe said the talks on Iran were to be "part of ongoing discussions".

US and German officials have said they do not expect any major announcements from the summit.

Britain, China, France, Germany, Russia and the US are expected to meet later this month to discuss reports from the International Atomic Energy Agency on Iran's compliance with international demands. 

Iran has refused to agree to UN demands to halt nuclear work that could have both civilian and military uses.
  
Mahmoud Ahmadinejad, the Iranian president, has said the nuclear programme is irreversible and that Tehran has 3,000 centrifuges in its underground Natanz plant.

Close ally

John Glenn of the German Marshall Fund, a US public policy and grantmaking institution, told Al Jazeera that one of the main purposes of the visit was to thank Merkel for being a good friend to the US.

"She has brought them [the US and Germany] together after a period of rancour, and most recently she managed the diplomacy of getting the renewal of the German mission in Afghanistan," he said.

Bush normally reserves invitations to his ranch for close allies and the invitation is a striking contrast to the frosty relationship Bush had with Merkel's predecessor, Gerhard Schroeder, who vocally opposed the Iraq war.

"In Texas, when you invite somebody to your home, it's an expression of warmth and respect and that's how I feel about Chancellor Merkel," Bush said before welcoming Merkel and her husband Joachim Sauer at the property's helipad.

The two leaders were also expected to discuss Afghanistan, the Middle East, Iraq, climate change, Myanmar, and the Doha trade round.