Secretary of State Hillary Clinton proclaimed a "new era for America" at her first day of work and said President Barack Obama would visit her Thursday to show a fresh unity of purpose.

Clinton, greeted by cheering crowds at the State Department, pledged that the Obama team would no longer "tolerate" the divisions that "paralyzed" the previous administration of president George W. Bush.

"I believe with all my heart that this is a new era for America," a beaming Clinton told hundreds of diplomats and others after being sworn in Wednesday as the 67th secretary of state.

Clinton, the wife of former US president Bill Clinton, faces unfinished wars in Iraq and Afghanistan, the troubled Middle East peace process, climate change, conflicts in Africa and efforts to revamp a tarnished US image.

"I think this is a time of such potential and possibility. I don't get up in the morning just thinking about the threats and the dangers, as real as they are. I also think what we can do," said Clinton.

She also sought to highlight the role of the US Agency for International Development (USAID) which aims to use aid to advance foreign policy goals -- something her predecessor Condoleezza Rice had been accused of neglecting.

"I will do all that I can, working with you, to make it abundantly clear that robust diplomacy and effective development are the best long-term tools for security America's future," said Clinton, who supervises USAID.

The 61-year-old former US first lady and former New York senator drew massive applause when she informed the crowd that Obama and Vice President Joe Biden will visit the State Department on Thursday.

"We want to send a clear and unequivocal message: This is a team, and you are members of that team," said Clinton, who narrowly lost to Obama in a bitter campaign to be the Democratic Party's candidate for the presidency.

Neither Clinton nor Obama can make progress on foreign policy "unless we make clear we are all on the American team," Clinton said.

"We are not any longer going to tolerate the kind of divisiveness that has paralyzed and undermined our ability to get things done for America," she said, alluding to troubles in the Bush administration.

Colin Powell, who served as secretary of state under Bush's first term, was sidelined in policy-making by both vice president Dick Cheney and defense secretary Donald Rumsfeld.

However, Clinton welcomed both "candor" and "a good debate" in shaping US foreign policy.

Congratulations poured in from allies.

Foreign Minister Frank-Walter Steinmeier of Germany, an ally which had seen US ties fray during the Bush presidency, sent a letter offering to work with Clinton on Middle East peace and halting Iran's nuclear ambitions.

Germany is one of six countries working together in a bid to persuade Iran to abandon its nuclear ambitions. Steinmeier has long called on Washington to consider direct talks with the leadership in Tehran.

At her Senate confirmation hearing a week ago, Clinton said the Obama administration would pursue "an attitude toward engagement (with Iran) that might bear fruit."

US-Iranian relations were severed in 1980, following the Islamic revolution and seizure of US diplomats as hostage.

Clinton also pledged to fight climate change and work immediately to pursue Arab-Israeli peace, following an Israeli military offensive in the Gaza Strip that has ended in a fragile truce.

State Department acting spokesman Robert Wood said Clinton would on Thursday telephone her foreign counterparts, receive an intelligence briefing, meet diplomatic security, and chat with various regional experts.