Defense Secretary Pete Hegseth is blocking the promotion of four Army officers to be one-star generals, a highly unusual move that has prompted some senior military officials to question whether the officers are being singled out because of their race or gender.

Two of the officers targeted by Mr. Hegseth are Black and two are women on a promotion list that consists of about three dozen officers, most of whom are white men, senior military officials said.

Mr. Hegseth had been pressing senior Army leaders, including Army Secretary Daniel P. Driscoll, for months to remove the officers’ names, military officials said. But Mr. Driscoll, citing the officers’ decades-long records of exemplary service, had repeatedly refused.....

The frustrations with Mr. Hegseth’s approach came to a boil last summer during a heated exchange between Ricky Buria, Mr. Hegseth’s chief of staff, and Mr. Driscoll about a separate promotion.

Mr. Buria chastised the Army secretary for selecting Maj. Gen. Antoinette R. Gant, a combat engineer who served in Iraq and Afghanistan, to take command of the Military District of Washington, said three current and former defense and administration officials familiar with the exchange. The command provides security and performs ceremonial duties in the nation’s capital, and its commander often appears alongside the president at Arlington National Cemetery.

Mr. Buria told Mr. Driscoll that President Trump would not want to stand next to a Black female officer at military events, the officials said.