Senate support for Trump education nominee Betsy DeVos weakens
Betsy DeVos testifies before the Senate Health, Education and Labor Committee confirmation hearing to be next Secretary of Education on Capitol Hill in Washington, U.S., January 17, 2017. REUTERS/Yuri Gripas

Public refusals on Wednesday by two U.S. Senate Republicans to support Betsy Devos, President Donald Trump's pick for education secretary, raised the possibility of a rare congressional rejection of a Cabinet nominee.

In an ominous sign for Trump, Republican senators Susan Collins and Lisa Murkowski said they would not vote for DeVos, a billionaire philanthropist and charter-school advocate.

Democrats, uniformly opposed to DeVos, are expected to oppose her as a block. They would only need for three Republicans to side with them to make DeVos just the 10th cabinet nominee in U.S. history to be rejected by Congress.

Soon after Collins and Murkowski staked out their opposition to DeVos, the White House said it is confident that she will ultimately be approved.

"I cannot support this nominee," Murkowski said in a floor speech saying she needed to make her intentions clear to her colleagues.

DeVos' nomination barely squeaked through a Senate committee vote on Tuesday, with both Collins and Murkowski saying they voted yes only so the entire Senate could debate the matter.

Trump's early nominations, primarily for security posts, had an easier time on Capitol Hill than names now before the Senate.

Republicans hold majorities in both the Senate and House of Representatives, but Democrats have been on a blitz to try to block the nominations, often raising concerns about conflicts of interest.

On Wednesday, the Senate Finance Committee had to suspend its rules to advance Treasury Secretary nominee Steve Mnuchin and Health Secretary nominee Tom Price to the full chamber for approval, the final step in the confirmation process.

Committee Democrats on Tuesday had boycotted the vote, forcing Republicans to scrap a requirement that at least one Democrat be present for a vote.

Confirmation hearings for Labor Secretary nominee Andy Puzder have been delayed over ethics filings.

Meanwhile, the Senate confirmed Rex Tillerson as secretary of state on Wednesday, filling a key spot on the national security team despite concerns about the former Exxon Mobil Corp chief executive officer's ties to Russia.

(Additional reporting by Susan Heavey; Editing by Kevin Drawbaugh and Alan Crosby)