Condoleezza Rice has begun her first day as US secretary of state pledging to place diplomacy at the heart of US foreign policy.
State department staff gave their new boss a warm welcome
Ms Rice, who was warmly applauded by staff as she arrived for work, declared that "history is calling us".
She said the state department would spearhead President Bush's vision of spreading democracy around the world.
Ms Rice's appointment was delayed until after a Senate debate that approved her appointment by an 85-13 margin.
"I know there are those who wonder whether democracy can take hold in the rocky soil of the West Bank or in Iraq or in Afghanistan," she said.
"That's our charge, that's our calling," she added.
Ms Rice said she looked forward to working with allies in a "great cause".
The BBC's Jonathan Beale at the state department says staff there will welcome Ms Rice's assertion that they will be in the forefront of US foreign policy.
That has not always appeared to be the case, he adds, and the department often seemed sidelined during Colin Powell's term.
While her stress on diplomacy may reassure some, it is clear that she shares the president's foreign policy goals of spreading democracy and freedom, our correspondent says.
Ms Rice, 50, arrived at work to a pre-planned schedule of telephone calls to foreign ministers and a White House meeting on Iraq.
Among the key issues she faces are the imminent elections in Iraq and the challenge of repairing key foreign alliances strained by the US invasion of the country in 2003.
Ms Rice is also expected to play a key role in shaping US policy towards North Korea and Iran, both suspected of harbouring nuclear ambitions.
Her warm reception among state department staff came after a hard-fought confirmation hearing in the US Senate.
Democrat senators forced a full debate on Ms Rice's appointment and she was questioned intently on her role as National Security Adviser during Mr Bush's first term in office.
Her appointment was opposed by 13 senators, the largest opposition to a secretary of state appointment in modern times.