"I want a diplomatic solution and I will make every effort to achieve it. I am sure that the US president will lend me his ear," Merkel said in an interview with the Berliner Zeitung newspaper.

She said the international community must stand together to stop Iran acquiring nuclear weapons, and if further sanctions were needed to pile pressure on Tehran, these should be agreed by Russia and China as well.

"The international community must pursue its goal of preventing Iran from having nuclear arms with firmness. This is a process we should take step by step.

"If the current talks are not successful, then Germany will also be willing to implement further, tougher sanctions."

Asked about adopting a sanctions regime without a UN Security Council resolution, Merkel said: "I continue to count on the unity of the international community, including Russia and China.

"The UN is the place where sanctions are negotiated. The more (countries) implement sanctions, the more effective the sanctions are," she said.

Merkel will arrive in Texas on Friday for a weekend of talks with Bush, who warned world leaders last month that they must prevent Iran from getting nuclear weapons "if you're interested in avoiding World War III."

Washington has refused to rule out the use of force if Iran's hardline regime continues to defy international pressure to halt sensitive nuclear work.

The Security Council has passed two rounds of sanctions to force Iran to suspend uranium enrichment, which can be used to supply the fuel for power generation or for nuclear arms.

Washington accuses Tehran of seeking a nuclear weapon, but the Islamic republic says it only wants to generate electricity for its growing population as fossil fuels run out.

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