Thomson Reuters
U.S. Secretary of Defence Mattis leaves a news conference after a NATO defence ministers meeting in Brussels
While en route to Seattle to meet with technology leaders and tour the Pentagon's Defense Innovation Unit-Experimental in Silicon Valley, Mattis was asked whether he knew Trump would make such a remark.
"I was not elected. The American people elected the President," Mattis said. "I think what he's pointing out is simply that - that these provocations - you can see his diplomatic effort to try and stop it.
"And he's just showing the concern he has, that is shared, obviously, globally, when you see that kind of unanimous Security Council result. That's what he's conveying," he added.
Mattis did not say whether he knew Trump warned him of the heated remark, although administration officials told Reuters it was "unplanned and spontaneous." On Thursday, Trump doubled down on his earlier remark, musing that perhaps it wasn't tough enough, according to the AP.
Mattis distanced himself from the line carefully, saying: "The rhetoric is up to the President. This is my rhetoric."
The secretary has become quite adept at this. At a cabinet meeting in June, where various officials went around the table mainly praising the president as reporters looked on, Mattis instead praised the troops he leads at the Department of Defense.