Moncef Slaoui, the chief adviser for Operation Warp Speed, has resigned but will be available to the incoming Joe Biden administration as a consultant for about four weeks, a Biden transition official told Reuters late on Tuesday.

Slaoui's role leading the Covid-19 vaccine development for the government effort is expected to be diminished after Jan. 20, according to CNBC, which first reported the development.

The Biden team has not asked Slaoui to stay past his current contract, which includes a 30 days' notice before termination, CNBC said.

The U.S. Department of Health and Human Services, which oversees Operation Warp Speed, did not immediately respond to requests for comment late Tuesday.

Slaoui, a former GlaxoSmithKline executive who had also served on the board of directors of Moderna Inc, was named last spring to spearhead the government's effort at developing a Covid-19 vaccine on an accelerated schedule.

According to Politico, Slaoui had said he planned to step down by early this year, but last week he said he "decided to extend that in order to ensure that the operation continues to perform the way it has performed through the transition of administration."