But Rice said on the second day of her Senate confirmation hearing that the government must ultimately speak to the world with a single voice and "we are one administration with the president in the lead."

During her four years as Bush's national security adviser and one of his closest aides, Rice was accused by critics of blindly following his hardline policies in Iraq and elsewhere in Washington's war on terror.

She denied this Wednesday, telling the Senate Foreign Relations Committee, "I have no difficulty telling the president exactly what I think. ... Sometimes he agrees, and sometimes he doesn't.

"The fact is that I felt very strongly that no one else should ever know the times when he disagreed and when he didn't."

The designated successor to Colin Powell as chief US diplomat said Bush expected her to provide "my most candid advice" and "argue vociferously" when she disagreed on policy matters.

"I will be a strong voice for what I believe and for what the State Department believes is the best course going forward," said Rice, 50, who is expected to be confirmed by the committee later Wednesday and by the full Senate on Thursday.

But she stressed that Bush would have the final word "as we decide how to try to use this time of diplomacy to build new structures and to bring old relationships to use, to pursue this new agenda."