By Kevin Liptak, CNN White House Producer

(CNN) -- Breaking his public silence about four American soldiers killed during an ambush in Niger, President Donald Trump said Monday he'd penned personal letters to their families and planned to phone them later this week.

He also claimed, without merit, that his predecessors hadn't written or called the families of slain American troops during their tenures, though the tradition of presidents reaching out after US servicemen are killed in action is long-established.

Trump said he'd written the letters over the weekend, and suggested they'd be mailed early this week. He was speaking 12 days after the ambush -- the deadliest combat incident since he took office.

"I felt very, very badly about that," Trump said during a press availability in the Rose Garden. "I always feel badly. It is the toughest calls I have to make are the calls where this happens, soldiers are killed."

He then claimed that other commanders in chief hadn't reached out to families of Americans killed in action, indicating he'd been told as much by the generals who serve in his administration.

"All I can do is ask my generals," Trump said. "Other presidents did not call, they would write letters, and some presidents didn't do anything."

"I like, when I can, the combination of a call and also a letter," he said.

Barack Obama, during his term in office, wrote letters and made calls to families of killed Americans, according to former administration officials. He also made frequent visits to the Walter Reed National Military Medical Center to spend time with wounded troops.

George W. Bush also wrote letters to families of troops killed in the wars in Iraq and Afghanistan, which began during his tenure.

When pressed about his assertion, Trump backtracked slightly.

"I don't know if he did," he said of Obama. "I was told that he didn't often, and a lot of presidents don't. They write letters. I do, I do a combination of both."

Trump's remarks Monday marked the first time he's commented at all -- in person or on Twitter -- about the Green Berets and US support personnel who were slain around the October 4 raid. The White House press secretary said previously the administration was still reviewing the circumstances around the mission.

"It is a very difficult thing," Trump said. "It gets to a point where you make four to five of them in one day, it is a very, very tough day."

Officials briefed on the Niger raid have described to CNN a scene of confusion and uncertainty in the immediate aftermath of the incident. Troops were left for nearly an hour before help could arrive to the remote area they were operating.

The White House has said little about Trump's involvement in the proceedings, and he did not travel to Dover Air Force Base for the return of the soldiers' bodies to the United States.

The brother of one of the men killed said on Monday that hearing from Trump was not high on his list of priorities.

"It's been the furthest thing from my mind and the minds of my family," said Will Wright, the brother of Staff Sgt. Dustin Wright, adding he bore no ill-will toward Trump.

After Trump's remarks on Monday, former Obama officials and other Democrats sharply criticized his remarks about his predecessors, calling them insensitive.

"The commander in chief told a totally irresponsible and disgusting lie in the Rose Garden today, claiming past presidents did not call the families of fallen servicemembers," said a spokesman for the Democratic National Committee, Brian Gabriel. "Trump's jaw-dropping, disrespectful lie is not based anywhere in reality and is another symptom of a deep-seated obsession with tearing down President Obama."

Responding to the backlash, White House press secretary Sarah Sanders insisted that Trump wasn't intending to criticize former commanders in chief

"The President wasn't criticizing predecessors, but stating a fact," Sanders said in a statement. "When American heroes make the ultimate sacrifice, Presidents pay their respects. Sometimes they call, sometimes they send a letter, other times they have the opportunity to meet family members in person."

"This President, like his predecessors, has done each of these," Sanders went on. "Individuals claiming former Presidents, such as their bosses, called each family of the fallen, are mistaken."