 -- The family of a U.S. Army captain who was killed while serving in Iraq in 2004 slammed President Donald Trump for "unbecoming behavior," after Trump said on Monday that past presidents never called the families of fallen soldiers.

In a statement to ABC News, Gold Star father Khizr Khan and his wife, Gazala Khan, said they were saddened by Trump's "selfish and divisive" actions and his lack of empathy, which they believe have undermined the dignity of the office of the presidency.

"One more time, he has shown us that he is undeserving of the leadership of our great nation," the statement read.

They also expressed their sympathy at the death of the four soldiers killed nearly two weeks ago in Niger.

"We stand with the families in their grief and pray for their strength and peace. And tell them that this nation will never forget the service and sacrifice the brave hero sons made on behalf of this great nation and for our liberty and safety; their families' service and sacrifice will also be always remembered. We stand with the families in this moment of grief," they said.

Trump walked back his initial statements in a radio interview on Tuesday morning.

"But I really speak for myself, I'm not speaking for other people. I don't know what Bush did, I don't know what Obama did," Trump said.

The Khans' son, Humayun Khan, was killed in 2004 while serving in Baqubah, Iraq. He was posthumously awarded a Bronze Star and a Purple Heart for saving the lives of other soldiers.

Khizr Khan gave an impassioned speech at the Democratic National Convention in July last year with his wife by his side, boldly calling for Trump to read the U.S. Constitution. Trump responded by belittling the family, and questioned why Gazala Khan didn't speak at the DNC like her husband did.

“If you look at his wife, she was standing there,” Trump said to ABC News chief anchor George Stephanopoulos. “She had nothing to say. She probably, maybe she wasn't allowed to have anything to say.”