David Miliband hinted to Hillary Clinton at his heartbreak and anger over losing the Labour leadership to his brother, her newly-released emails have shown.
Miliband emailed Clinton, with whom he worked as foreign secretary when she was secretary of state, just days after losing the 2010 contest.
He thanked her for her "best wishes" and telling her a recent message was "poignant".
"Losing is tough," he wrote. "When you win the party members and MPs doubly so. (When it's your brother...)"
Miliband said it was 'doubly' difficult to stomach losing out to Ed when he had the most party members and MPs
He adds: "I am so proud of the campaign we ran, the issues we raised, etc. We got people to believe in a New Labour platform - and modernised the platform."
The next paragraph is partly redacted. It begins: "I have announced today that I will stay in Parliament."
After the redaction, he signs off: Thanks for all your encouragement over the years. I will let you know when I am in DC."
His email address is partly redacted but it begins 'D.Gunners', reflecting his support of Arsenal.
The email is among the 7,000 pages published from Clinton's private address that she used for correspondence on a range of political topics, including the Middle East, who will run for president and members of the American congress.
One email from Clinton advisor Huma Abedin is entitled: 'Ed Miliband Is New Leader Of The UK Labour Party.
It is one word long: "Wow."