BERLIN, May 11 (Xinhua) -- German Chancellor Angela Merkel on Friday criticized the United States for leaving the Iran nuclear deal unilaterally.

"This breaks the trust in the international order," she said in the western German city of Muenster.

Although the deal was far from ideal and many issues still remain unresolved, the U.S. withdrawal is a cause of great concern and regret, she said.

U.S. President Donald Trump on Tuesday announced his decision to pull the United States out of the 2015 landmark agreement, ignoring repeated opposition from western allies.

Foreign ministers from the European Union (EU) member countries are expected to hold a crisis meeting with Iran in London on Monday in a bid to save the deal, the Guardian newspaper reported Thursday.

The Iran agreement, formally known as the Joint Comprehensive Plan of Action, was signed between Iran, the five permanent members of the UN Security Council (China, the U.S., UK, France and Russia), Germany and the EU.