Former President Barack Obama's deputy chief of staff for operations called President Trump a "deranged animal" after he claimed his predecessor "didn't often" call the families of fallen service members.

"That's a fucking lie," Alyssa Mastromonaco tweeted in response to Trump's claim Monday. "To say president obama (or past presidents) didn't call the family members of soldiers KIA — he's a deranged animal."

that's a fucking lie. to say president obama (or past presidents) didn't call the family members of soldiers KIA - he's a deranged animal. — alyssa mastromonaco (@AlyssaMastro44) October 16, 2017

Trump said Monday he wrote letters to the families of the four soldiers killed in Niger, adding that he planned to eventually call them "when it's appropriate."

"President Obama and other presidents, most of them didn't make calls. A lot of them didn't make calls," Trump said at an impromptu news conference in the Rose Garden.

Related: Trump claims Obama 'didn't often' call families of fallen service members

Trump was later asked to clarify the claim about Obama.

"President Obama I think probably did sometimes, and maybe sometimes he didn't. I don't know," he added. "That's what I was told. All I can do is ask my generals. Other presidents did not call. They'd write letters and some presidents didn't do anything, but I like the combination of — I like, when I can, the combination of a call and also a letter."

The four soldiers were killed Oct. 4, and Monday marked Trump's first public comments on the deaths. The Pentagon has yet to identify which group is responsible, but the attack is suspected to have come from an affiliate of the Islamic State.

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