US President Barack Obama was expected to announce his nomination of White House chief of staff and budget expert Jack Lew as his next Treasury secretary on Thursday, a White House official said.

Lew, 57, will take the lead on difficult negotiations with Congress on how to cut the nation's looming debt and rein in spending - a central challenge in Obama's second term.

Lew is expected to be confirmed by the Senate. He will take over from Timothy Geithner, who was slated to attend Thursday's announcement, the White House official said.