Trump went to the Arlington National Cemetery just outside Washington with family members of some of the 13 service members killed in a 2021 bombing during the last hours of the US withdrawal from Afghanistan.

His campaign posted photos from the visit, including one showing him giving a thumbs-up gesture while standing with relatives at the grave of one of the Marines killed.

The Army said an Arlington employee was "abruptly pushed aside" when she sought to ensure a law prohibiting political activity on cemetery grounds was followed.

"This incident was unfortunate, and it is also unfortunate that the (Arlington National Cemetery) employee and her professionalism has been unfairly attacked," an Army spokesperson said in a statement.

Going on the offensive, Trump's campaign co-manager Chris LaCivita has described the employee as a "despicable individual," while campaign spokesman Steven Cheung said she was "clearly suffering from a mental health episode."

Trump has made criticism of President Joe Biden's handling of the US retreat from Afghanistan a key note of his campaign ahead of the November election.

The withdrawal was made as part of a peace deal signed by the Trump administration with the Taliban.

Uproar over the incident at Arlington on Monday is the latest controversy in Trump's troubled relationship with the military.

While often touting his support for the armed forces, he privately mocked the war dead while president and did not want to be seen near military amputees, according to his former chief of staff.