Washington DC - President Donald Trump used a Veterans Day commemoration Wednesday to defend the war against Iran – an increasingly unpopular conflict that helped trigger a Democratic takeover of Congress in last week's midterm elections.

"The bravery and skill of our amazing American warriors has absolutely been incredible," Trump said in an address at Arlington National Cemetery just outside Washington.

"When this conflict is over, and it will be soon, the entire world will be a much safer and better place, more peaceful place, and a place without the kind of danger that we had to suffer."

The war, which began on February 28 with US and Israeli strikes against Iran, has so far cost the lives of 23 US service members and wounded several hundred more, according to the latest Pentagon figures.

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Trump said in his remarks that the conflict was started not by Washington but by Tehran, which "has been waging war on America since 1979." He stressed that US forces were acting in order to halt Iran's capacity to build a nuclear weapon.

During his speech before troops, veterans and top officials in his administration, Trump name-checked Defense Secretary Pete Hegseth, who was in attendance, saying he had "done a fantastic job."

Republicans in the House of Representatives on Tuesday blocked an effort – launched by an outgoing Republican lawmaker – to impeach Hegseth for allegedly waging war without congressional authorization and abusing his powers as Pentagon chief.

Trump (80) attended a wreath-laying ceremony at the cemetery's Tomb of the Unknown Soldier, a sacred symbol for America's lost service members.

During his remarks, Trump brought up the issue of the 250-foot-tall triumphal arch he hopes to build just outside the cemetery, saying it would be dedicated "soon."

On Tuesday, the family of John F. Kennedy asked a court to prevent its construction, arguing the massive structure would block views of and cast shadows over the gravesites of the slain president and other Kennedy relatives buried at Arlington National Cemetery.

The project also faces lawsuits from a group of veterans, the city of Washington and the state of Virginia.