Former US secretary of state Hillary Clinton called Chancellor Angela Merkel "the greatest leader in Europe” during a visit to Berlin yesterday and said it was high time America had a woman leader too, though without confirming she would seek the job.

Hillary also referred to Russian President Vladimir Putin as a "tough customer with a pretty thin skin" in an appearance at a Berlin theatre to promote her new book, “Hard Choices".

The former senator and wife of ex-President Bill Clinton is widely expected to run for the White House in 2016 and has cited Merkel as a good argument for the United States having a woman president soon.

■ I think we are ready for a woman to break through the glass ceiling," she said in an interview with Bild am Sonntag newspaper, adding that she would decide whether to run for president "at the end of this year or early next year".

Hillary joked at the Schiller Theater about her and Merkel's shared taste for pants suits and voiced admiration for the chancellor's leadership of Europe in the euro zone debt crisis.

"I say in the book I think she is the greatest leader in Europe, I think she is a great leader globally, I think she carried Europe on her shoulders and it wasn't easy," she said.

The book has kept the former US senator and first lady hopping from event to event across the United States and Canada.