Angela Merkel insists on new sanctions against Iran

"Iran should realise that we're taking it very seriously," Merkel said at a news conference with French President Nicolas Sarkozy in Berlin.

"We've decided that we'll discuss further sanctions in September if...there is no clear statement from Iran," she said.

U.S. President Barack Obama has given Iran until September to take up a six powers' offer of talks on trade if it shelves nuclear enrichment or face harsher penalties.

Last week Merkel said Iran could face new sanctions in the energy and financial sectors if it does not show a willingness to negotiate on its nuclear programme.