John Kerry, who has been officially sworn in as the new US Secretary of State, said America would "do what was necessary" to stand up to "extremism, terrorism, chaos and evil".
John Kerry hailed the contribution of outgoing Secretary of State Hillary Clinton at his official swearing in ceremony in Washington.
"I want to thank Secretary Clinton for the unbelievably high standard of energy, commitment and vision that she set in her superb stewardship of the US State Department," said Kerry.
The new Secretary of State also paid tribute to Barack Obama, saying: "The President has restored American's place and our reputation in the world."
John Kerry has been sworn in as US Secretary of State, replacing Hillary Clinton.
Vice-President Joe Biden, swearing in his longtime friend, said: "Few men or women I have ever worked with have more integrity or honour than John Kerry."
Kerry quipped: "I've grown used to being sworn at, it's really nice to be sworn in."
Democrat politician John Kerry is in Washington DC at a ceremonial swearing in for his new role as US Secretary of State.