Ed Miliband is hoping his "brush-by" visit with Barack Obama will show he is ready to lead Britain on the global stage.
Ahead of his visit to the White House, the Labour leader says he is determined to create a "post-Iraq" relationship with the United States.
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Some 66 people have been killed after the plane they were travelling on crashed in southern Iran.
The letter calls for an end to harassment, abuse, and impunity in a world "ripe for change".