President Barack Obama will nominate Jack Lew as Treasury secretary as early as Thursday, making him his point man in the coming battle over the debt ceiling, a source familiar with the process told CNBC.
In another move, Labor Secretary Hilda Solis announced plans Wednesday to step down from the position she assumed in 2009.
Lew, the White House chief of staff and former director of the Office of Management and Budget, would succeed Timothy Geithner, who has been planning to step down.
A source told CNBC that Deputy National Security Adviser Denis McDonough was a leading candidate to succeed Lew as chief of staff.
Lew's expected appointment would be subject to confirmation by the Democratic-controlled Senate.
Despite the agreement to end the battle over the "fiscal cliff" at the start of the year, the White House and Republicans are still locked in a fight over the debt ceiling and demands for spending cuts.
A new analysis by the Bipartisan Policy Center said the U.S. government could exhaust its ability to meet all its financial obligations as early as Feb. 15. (Read More: Get Ready: US May Hit Debt Ceiling by Mid-February)
Lew, 57, would lead the administration's efforts, but Republicans perceive him as partisan. (Read More: Lew Faces a Big Test in Fiscal Talks)
"He is not the sweet-talker that Tim Geithner is to Republicans," James Pethokoukis of the conservative American Enterprise Institute, said on CNBC's "Kudlow Report" on Tuesday night in anticipation of the expected appointment.
Lew served as President Bill Clinton's OMB director from 1998 to 2001 and was an aide to the late Democratic House Speaker Tip O'Neill.
"The easy thing about him is you think he's like some sort of technocrat," Pethokoukis said. "He's far more ideological than that. ... And he does not have Tim Geithner's ... experience in markets."
"What you really have is a lifelong budgeteer whose main job appears is to give Republicans fits in these negotiations," Pethokoukis said.
The nomination would be Obama's third controversial pick this week. On Monday, he nominated Chuck Hagel as Defense secretary and John Brennan to head the CIA. (Read More: No More Mr. Nice Guy: New Battles Ahead for Obama)
Hagel has faced tough criticism from congressional Republicans who say the former GOP senator is anti-Israel and soft on Iran.
Brennan, a 25-year CIA veteran, withdrew from consideration for the spy agency's top job in 2008 amid questions about his connection to enhanced interrogation techniques during the George W. Bush administration.
Obama also has nominated Sen. John Kerry to succeed Hillary Rodham Clinton as secretary of state.
As an observant Jew, Lew doesn't work on Friday nights or Saturdays.