John Kerry starts first day at US state department
John Kerry has begun his first day as US secretary of state, pledging that the security of staff was his priority.
Referring to his predecessors Hillary Clinton and Condoleezza Rice, Mr Kerry, 69, joked: "Can a man actually run the state department?"
In a speech to staff, he joked that he has "big heels to fill".
The former Massachusetts senator and 2004 Democratic presidential candidate was greeted with applause from foreign service workers.
Mr Kerry was greeted on Monday in the large black-marble lobby of the state department in Washington DC by a cheering crowd of employees.
He thanked his predecessor, Mrs Clinton, for helping to restore America's reputation.
Mr Kerry also addressed the deaths of four Americans, in an attack on the US consulate in Benghazi, Libya on 11 September, a security failure for which Mrs Clinton accepted responsibility.
Addressing his new staff, Mr Kerry said he understood "how critical it is that you have somebody there advocating for you. The dangers could not be more clear".
"I pledge to you this: I will not let their patriotism and their bravery be obscured by politics," he said.
"I guarantee you that, beginning this morning, when I report for duty upstairs, everything I do will be focused on the security and safety of our people," Mr Kerry added.
But he also appealed to employees for their help, saying the work of the state department could "make the world more peaceful".
Mr Kerry, who chaired the foreign relations committee during his 28 years in the Senate, said the Foreign Service was in his genes.
He recalled his childhood growing up in Berlin, and produced a copy of his first diplomatic passport as the 11-year-old son of an American diplomat.
Mr Kerry described exploring Berlin by cycle as a boy, adding: "That was a great adventure, and I will tell you, 57 years later, today, this is another great adventure."
Correspondents say the new state department head will spend much of the week getting in touch with foreign leaders.
At the weekend, he spoke to Israeli Prime Minister Benjamin Netanyahu and Palestinian Authority President Mahmoud Abbas.
Mr Kerry also contacted the foreign ministers of Japan, South Korea, Turkey, Canada and Mexico.
He succeeds Mrs Clinton as the top US diplomat.
Mrs Clinton, who stepped down on Friday, left the post after four years, visits to 112 countries and nearly a million air miles.
The former first lady is tipped as a possible candidate for the 2016 presidential election.