Former US president Donald Trump has mocked his Republican rival Nikki Haley over the absence of her husband, who is deployed overseas, drawing a sharp reaction from the Indian-American politician who said the person who disrespects military families has no business being commander-in-chief.

Haley's husband Major Michael Haley, a commissioned officer with the South Carolina National Guard, is currently on a year-long deployment with the 218th Maneuver Enhancement Bridge, which is providing support in the Horn of Africa. He deployed in June.

The war of words between two Republican presidential candidates started with a Trump rally on Saturday in South Carolina where the 77-year-old former president, seemingly unaware of his deployment, when started questioning his whereabouts “Where’s her husband? Oh, he’s away. … What happened to her husband? Where is he? He’s gone,” Trump said at his rally in Conway in South Carolina, his first visit to the state this year.

Haley, 52, the only candidate against Trump in the Republican Party's nomination race, fired back at Trump’s comments later on Saturday.

“Donald, if you have something to say, don’t say it behind my back; get on a debate stage and say it to my face,” she told a crowd in South Carolina.

“I am proud of Michael’s service. Every military family knows it’s a sacrifice. I have long talked about the fact that we need to have mental competency tests for [politicians] over the age of 75," she said.

Trump claims he would pass that – maybe he would, maybe he wouldn’t, she said.

"But if you mock the service of a combat veteran, you don’t deserve a driver's license, let alone to be president of the United States," she said.

“Michael is deployed serving the US country, something you know nothing about. Someone who continually disrespects the sacrifices of military families has no business being commander-in-chief," Haley said.

Trump’s comment on Haley’s husband also drew criticism from various quarters.

“Only a sick individual would put down a service member who is deployed. This disrespects every military family in our country. It’s exactly the chaos we don’t need in America,” said General (rtd) Don Bolduc.

In a rare move, Michael Haley fired back at the former president, posting a meme on Twitter reading, “The difference between humans and animals? Animals would never allow the dumbest ones to lead the pack,” while mentioning Trump’s account in the caption.

Continuing his attack, Trump alleged that Haley is the candidate of globalists and warmongers who want to spend trillions and trillions of dollars on endless wars.

“The radical left Democrats want Nikki Haley because they know that she's easy to beat. She's very easy to beat. Haley supports a 23% national sales tax, and she wants to gut Medicare and Social Security...," he said.

Earlier, Haley kicked off her “Beast of the Southeast” bus tour with a stop in Newberry.

In an interaction with the media, she spoke about her opponents’ lack of stamina and stressed the importance of mental competency tests for politicians over the age of 75.

Her campaign also distributed examples of the mental competency tests used by medical professionals, demonstrating that it should not be a difficult test for those who are seeking the highest office in the land.

“(For months) I have always said that (President) Joe Biden was not going to be president. You look at what’s happened in the last couple of days, and you see exactly what I’m talking about. The fact that we’re dealing with someone who the special counsel said that their memory was failing, that they are diminished…,” she said “It’s bigger than just Joe Biden. You can look at the same thing: whether it’s Donald Trump getting me confused with Nancy Pelosi, his temper tantrums, the things he’s done,” Haley said.

In a damaging report, a special US counsel last week said that President Joe Biden “willfully” mishandled classified documents as a private citizen but concluded that it would be difficult to convict him as he comes across as an “elderly man with a poor memory”.

The report from Special Counsel Robert Hur has prompted an election-year brawl and renewed questions about Biden's advanced age.

“It’s time for a new generational leader. The party that dismisses their 80-year-old candidate is the party that will win the presidency, without a doubt. The Democrats are waking up to that now. You’re going to see them make their moves,” she said.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.