Abu Dhabi: US Secretary of State and former presidential candidate John Kerry declared on Wednesday that Hillary Clinton "will make a terrific president."
Speaking on a flight from Beijing to Abu Dhabi, Washington's top diplomat told reporters: "As a father of two daughters, I'm proud."
Kerry was Clinton's successor at the State Department after she left to prepare her bid to become the Democratic presidential nominee.
And he has some idea what she is up against, having himself tried and failed to win the White House for the party in the 2004 campaign.
On Tuesday, Clinton all but guaranteed herself the nomination with victories in the Democrats' last major primary races, including California.
Her opponent, Vermont senator Bernie Sanders, has yet to concede but appears to have no practical way to beat her convention delegate count.
President Barack Obama has congratulated Hillary and now Kerry, who has been reluctant to intervene in the campaign, has lent his support.
"I have great respect for the election process which is why I didn't say anything until people had voted last night," he said.
"But that said, I believe that she is in tune with and in touch with major issues... I think she's a great candidate. The American people will decide."
Kerry said he was particularly pleased that Clinton is the first woman chosen as a major party nominee, dubbing this "a truly historic moment."