Republican National Committee Chairman Michael Steele's comments come on the same day Sebelius, the Democratic governor of Kansas, vetoed a bill that would rewrite a state law restricting late-term abortions. The measure would have required doctors performing such abortions to report additional information to the Kansas Department of Health and Environment.
Steele says Sebelius has not been forthcoming about her stance on late-term abortions and her ties to a Kansas abortion doctor, George Tiller.
"Significant questions remain about Gov. Kathleen Sebelius' evolving relationship with a late-term abortion doctor as well as about her position on the practice of late-term abortions," Steele said in a statement. "If Gov. Sebelius and the Obama administration are unwilling to answer these questions, President Obama should withdraw her nomination."
Steele says the Senate should not vote, nor should Sebelius be confirmed, until questions are answered completely.
"This is nothing more than a baseless attack from someone desperate to stake a claim as the leader of the leaderless Republicans and get right with the right-wing of his party," said Reid spokesman Jim Manley.
Steele's statement came as Republicans blocked immediate action on Sebelius' confirmation in the Senate, likely pushing a final vote to next week at earliest. Supporters had hoped for faster action, but Democrats remain confident they have enough votes to get Sebelius confirmed.
Sebelius was approved by the Senate Finance Committee this week with just two of 10 GOP votes. Several Republicans, including the top committee Republican Chuck Grassley of Iowa, raised concerns about her initial failure to disclose to senators how much campaign money she got from Tiller.
When the discrepancy became public Sebelius acknowledged getting an additional $23,000 from Tiller and his abortion clinic beyond the $12,450 she initially reported. She apologized and said it was an inadvertent error.
That happened after Sebelius breezed through her Finance Committee confirmation hearing early this month without a single senator raising the topic of abortion. Republicans had some cover on the issue because Sebelius was supported by both her home-state GOP senators, including Sen. Sam Brownback, a strong abortion opponent.
But since then opposition from anti-abortion activists -- and pressure on Republican senators -- has grown.
Sebelius told the Finance Committee that she personally opposes abortion, but she also has a long record in Kansas politics of supporting abortion rights. She's repeatedly vetoed legislation sought by anti-abortion groups to impose more regulations on abortion clinics and rewrite the state's restrictions on late-term abortions.
Steele, meanwhile, has had problems of his own on abortion as he's sought to firm up his conservative bona fides since becoming GOP chairman earlier this year. Last month he insisted he was "pro-life" after a magazine quoted him as saying abortion was "an individual choice."