WASHINGTON (Reuters) - The U.S. federal human resources agency at the heart of billionaire Trump adviser Elon Musk's efforts to slash the federal workforce on Friday canceled a contract it had awarded to Workday.

The contract for a new cloud-based HR platform, signed on May 2, was awarded without seeking bids from rivals and had raised eyebrows among current and former employees of the Office of Personnel Management.

They had described the sole-source contract as unusual, given the competition in an industry that includes ADP and SAP, and expressed surprise to see OPM's largely successful in-house HR platform on track to be replaced.

On Friday, a federal contracting website page about the award was updated to state that the award opportunity was canceled, without elaborating.

OPM and Workday did not immediately respond to requests for comment. OPM said earlier this month that the sole-source award was necessary due to "operational failures" and federal mandates that required immediate action.