Republican presidential hopeful Mike Huckabee has slammed US President Barack Obama for nominating an openly gay man to lead the American Army.

In a statement released by his campaign, the former Arkansas governor accused Obama of prioritising the demands of homosexuals rather than strengthening the US military by nominating Eric Fanning, an openly gay man, to be the Army's top official.

"It's clear President Obama is more interested in appeasing America's homosexuals than honouring America's heroes," Huckabee said.

The Republican presidential aspirant added that Obama did not contribute to finding solutions to the challenges being faced by the military by nominating Fanning.

"Veterans suicide is out-of-control and military readiness is dangerously low, yet Obama is so obsessed with pandering to liberal interest groups he's nominated an openly gay civilian to run the Army," Huckabee said.

He also called on Obama to stop treating the US Army as a social experiment to accommodate homosexuals.

"Homosexuality is not a job qualification. The US military is designed to keep Americans safe and complete combat missions, not conduct social experiments," the former Arkansas governor said.

Obama announced on Friday his nomination of Fanning, who may become the first openly gay secretary of a US military branch if confirmed by the Senate.

The US President, who has long advocated the rights of homosexuals, cited Fanning's track record as his reason for making the nomination.

"Eric brings many years of proven experience and exceptional leadership to this new role," Obama said in a statement Friday.

"I am grateful for his commitment to our men and women in uniform, and I am confident he will help lead America's soldiers with distinction," he added.

Fanning has been the Army's acting secretary since June. He also once served as chief of staff to Secretary of Defense Ash Carter, and as undersecretary of the Air Force.

Another Republican presidential aspirant, Texas Senator Ted Cruz, meanwhile, said that Obama's choice of Fanning as next Army Secretary should not just be a "political statement."

"I certainly hope that the secretary of the Army is being nominated because the President wants the right person to defend our nation and not because he is looking to make a political statement on issues of sexual orientation unrelated to defending this nation and keeping us safe," Cruz said.

"But as I said, I will wait until his confirmation hearing to assess his record on the merits," he added.