Several senators voiced concern about her role in the run-up to the Iraq war.

"As a principal architect of our failed policy (in Iraq), Dr Rice is the wrong choice for Secretary of State," said Democrat Senator Edward Kennedy.

Despite the criticism, the Senate is expected to confirm Ms Rice as Secretary of State on Thursday.

Last week, the Senate Foreign Relations Committee gave their approval for her nomination to the post.

Republican back-up

Several Democrats who spoke on the Senate floor on Tuesday voiced concern that Ms Rice had misled the public about the justification for war on Iraq.

However, a number of Republican Senators spoke out in defence of Ms Rice's nomination.

"Outlaw regimes must be confronted. Dangerous weapons proliferation must be stopped. Terrorist organisations must be destroyed. Dr Rice has both the ability and the experience to meet these daunting challenges," said Senate Majority Leader Bill Frist.

BBC State Department correspondent Jonathan Beale says some Democrats see this debate as an opportunity to reflect the nation's growing unease about the US presence in Iraq.

However, there is little doubt that Ms Rice will be approved to take over from outgoing Secretary of State Colin Powell.