Condoleezza Rice, President George W Bush's nominee as secretary of state, says she will use diplomacy to reach a balance of power in the world.
Rice will have to unveil her own vision of the world
"Our interaction with the rest of the world must be a conversation, not a monologue," Ms Rice told the Senate during her confirmation hearing.
Iraq was high on the agenda of the session expected to last two days.
Ms Rice, 50, is close to President Bush - and is expected to be easily confirmed as Colin Powell's successor.
The hearings begin as Mr Bush prepares to be sworn in for his second term.
The BBC's Justin Webb in Washington says nobody is entirely sure which foreign policy camp Ms Rice belongs to.
As the president's national security adviser, her job has been to co-ordinate other people's input, rather than being a strong voice herself, our correspondent says.
But senators at the committee have been asking Ms Rice detailed questions to elicit her own opinions and judgements.
"We must use American diplomacy to help create a balance of power in the world that favours freedom," Ms Rice, 50, told the Senate Foreign Relations Committee.
"And the time for diplomacy is now."
She praised the leadership of President Bush in the aftermath of the 11 September 2001 attacks - "a defining moment for our nation and the world".
She said: "Under the vision and leadership of President Bush, our nation has risen to meet the challenges of our time: fighting tyranny and terror, and securing the blessings of freedom and prosperity for a new generation."
"Now is the time to build on these achievements to make the world safer, and to make the world more free."
RECENT SECRETARIES OF STATE
Colin Powell: 2001-2004
Madeleine Albright: 1997-2001
Warren Christopher: 1993-1997
James Baker: 1989-1992
George Schultz: 1982-1989
But she indicated that the US would not let traditional allies or multilateral institutions stand in the way of "effective" action by Washington.
Ms Rice's speech also focused on President Bush's vision for the solving the Israeli-Palestinian conflict.
"President Bush has broken with six decades of excusing and accommodating the lack of freedom in the hope of purchasing stability at the price of liberty. The stakes could not be higher," she said in her prepared remarks.
"As long as the broader Middle East remains a region of tyranny and despair and anger, it will produce extremists and movements that threaten the safety of Americans and our friends."
Senators were particularly interested to know what Ms Rice's Iraq policy would be - whether the US had enough troops and whether it had an exit strategy.
Ms Rice said the US had to remain engaged after the Iraqi election on 30 January including improving the Iraqis' ability to defend themselves and Iraqi leadership capacities.
Ms Rice is a trusted member of President's Bush innermost circle - some describe her as almost family, correspondents say.
She is also said to share many of his views, and is described as driven and highly ambitious.
Mr Bush is due to be sworn in on Thursday.