Cruz, speaking a Tea Party rally in Cedar Rapids, Iowa, last week, suggested that the United States should nuke Daesh-controlled territory in Iraq and Syria.
"We will utterly destroy ISIS. We will carpet bomb them into oblivion. I don't know if sand can glow in the dark, but we're going to find out," Cruz was quoted as saying by the Des Moines Register.
On Wednesday, while testifying before the Senate Armed Services Committee, US Air Force General Paul Selva was pressed for his take on Cruz's proposal. Selva appeared to agree with Senator Claire McCaskill's concerns about civilian casualties in such an attack.
Additionally, the general said using nuclear weapons would feed Daesh's narrative of an "apocalyptic war with the West." Such calls for nuclear strikes run counter to America's national security interest, he continued, and the US military does not now, and will not in the future, engage in carpet bombings.
Wednesday marked the second time in as many days the Pentagon faulted a GOP presidential candidate's policy suggestions. On Tuesday, the Pentagon criticized Donald Trump's call to ban Muslims from entering the United States, warning it played into Daesh's recruitment message of a war between the United States and Islam as a whole.
While Trump has been leading the polls, many consider Cruz to be a more viable GOP candidate for the White House.