Speaking on CNN’s “Starting Point,” Barrasso said Rice gave “bad information” when she initially blamed the deadly Sept. 11 attack on the U.S. Consulate in Libya on a spontaneous anti-American protest.
"She just parroted information she was given. A secretary of State needs to have sound judgment, ask tough questions, and should not be willing to just read talking points," Barrasso said. "You need to be thoughtful and ask the tough questions before speaking and she just didn't do that. To me that disqualifies her."
The White House later acknowledged that the assault, which claimed four American lives, was a planned terrorist attack.
Barrasso’s comments come after Rice, who is seen as a possible replacement for Secretary of State Hilary Clinton in a second Obama term, met with top Republicans on Capitol Hill this week to answer questions about her handling of the Benghazi attack.
But Rice’s effort to win over GOP lawmakers has had mixed results, with Sens. John McCain (Ariz.), Kelly Ayotte (N.H.) and Lindsey Graham (S.C.), who have been sharply critical of her, saying they were more “troubled” by her actions after their talks.
On Wednesday, two centrist Republicans, Sens. Susan Collins (R-Maine) and Bob Corker (R-Tenn.), met with Rice, but said they needed more information from her before they could commit to supporting her for the nation’s top diplomatic post.
But while many GOP senators, including Barrasso, have said they would try to block her nomination, Rice would likely need only a handful of Republican votes to overcome a filibuster if Democrats chose to support her.
President Obama has stood by his ambassador, praising her work as “extraordinary.”
“I couldn't be prouder of the job she's done,” Obama told reporters on Wednesday.
Democrats have pushed back against criticism of Rice, saying that she had shared the intelligence reports given to her and denying claims that she misled the public.
Rep. Adam Schiff (D-Calif.), who also appeared on CNN, said it was "unfair" for Barrasso and other Republicans to go after Rice.
"It’s unfair and unjustified to go after the U.N. ambassador for not asking deeper questions or probing the intelligence that was given to her by the CIA," Schiff said. "After all, let's not forget that the director of the CIA himself at the time as well as the director of National Intelligence, the top intelligence officials of the nation, both believed that when she went on the talk shows, they believed it began as a protest.
“Now they were wrong and the intelligence community were wrong, but I hardly think it's fair to suggest that the U.N. ambassador had better intelligence somehow than the head of the CIA and the director of National Intelligence."