WASHINGTON — Defense Secretary Mark T. Esper recused himself from reviewing a controversial $10 billion cloud-computing contract because his son works for one of the contract’s original bidders, the Defense Department said on Tuesday.

The decision removes Mr. Esper from a fierce lobbying battle between Amazon Web Services, the dominant player in the field of cloud computing, and Oracle. President Trump himself has weighed in over the 10-year contract to transform the military’s computing systems, making clear his own hostility toward Amazon and its founder, Jeff Bezos.

“Out of an abundance of caution to avoid any concerns regarding his impartiality,” the defense secretary has delegated decision-making concerning the contract, known as JEDI, to the deputy defense secretary, David L. Norquist, a Pentagon spokesman, Jonathan Hoffman, said in a statement.

The statement attributed the recusal to Mr. Esper’s “adult son’s employment with one of the original contract applicants,” but did not specify the company. The statement also did not identify the adult son by name, but the LinkedIn page for Mr. Esper’s son Luke Esper describes him as a digital strategy consultant at IBM, which was an original bidder for the contract.