After falsely accusing former US presidents of not calling the families of fallen soldiers, President Trump on Tuesday called the four families of American troops ambushed two weeks ago in Niger, the White House said.

"President Trump spoke to all four of the families of those who were killed in action in Niger," White House press secretary Sarah Huckabee Sanders said in a statement. "He offered condolences on behalf of a grateful nation and assured them their family's extraordinary sacrifice to the country will never be forgotten."

The phone calls came a day after Trump revealed in a press conference that he hadn't called the families because he wanted "a little time to pass." Thirteen days had passed since the October 4 ambush.

During the remarks, Trump also made a claim that previous presidents, including Barack Obama, didn't make calls to the families of soldiers who had died.

"The traditional way if you look at President Obama and other presidents, most of them didn't make calls. A lot of them didn't make calls," Trump said in the White House Rose Garden.

Alyssa Mastromonaco, a former aide to President Obama, called the claim "a fucking lie" on Twitter.

Mastromonaco, a former White House deputy chief of staff for operations in the Obama administration, added: "to say president obama (or past presidents) didn't call the family members of soldiers KIA - he's a deranged animal."