US President Joe Biden has slammed his predecessor Donald Trump for dragging Indian-American Republican presidential candidate Nikki Haley's husband into the swirl of personal attacks.

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.

Trump at a rally in South Carolina on Saturday questioned the whereabouts of Michael Haley.

“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.

“The answer is that Major Haley is abroad, serving his country right now. We know he thinks our troops are 'suckers,' but this guy wouldn’t know about service to his country if it slapped him in the face,” Biden said in a tweet on Sunday.

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

“Donald Trump’s comments represent a pattern of disrespect to every military member who sacrifices for us and the families who sacrifice alongside them,” she told Face The Nation CBS on Sunday.

“Military service is an incredible sacrifice, not only by those in uniform but also the families who stand behind them. I am grateful for every single one of you,” she said.

“I’m running for president because my husband, Michael, and his military brothers and sisters put their lives on the line to fight for our country. We should be willing to fight for our country here at home,” Haley said Sunday.

"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 on Saturday.

“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.

Conservatives and liberals alike are covering Trump’s attack on military families, and they agree: “This is trash.” As a result, Trump is taking heat for his comments.

“Donald Trump understands absolutely nothing about what it means to serve this country. This disrespect of Nikki Haley’s husband demonstrates again why he isn’t fit to be president,” said Navy Combat Veteran and retired NSA astronaut Captain Mark Kelley.

“Nikki Haley denounces Trump’s NATO comments and defends her husband against his attacks,” The New York Times said.

“I am old enough to remember a Republican Party where going after someone’s husband serving abroad would have been disqualifying,” CNN’s Jake Tapper said.

“This is trash,” said Mary Katharine Ham, host of the “Getting Hammered” pod.

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