It followed the Defense secretary's opening remarks to a Senate panel that the Pentagon "supports fully" Secretary of State Rex Tillerson's ongoing "efforts to find a diplomatic solution [to the North Korean threat] but remains focused on defense of the United States and our allies."
Rhode Island Democratic Sen. Jack Reed, ranking member of the Senate Armed Services Committee, said Mattis' comments about the DOD supporting diplomatic efforts toward Pyongyang "does not seem to be translated to the president." Reed said Trump "has in several tweets suggested that Secretary Tillerson's opening of [diplomatic] channels and preparing to discuss issues, directly and indirectly, is essentially a waste of time."
Reed asked Mattis, "How do you respond to those types of [tweets]. On one hand, you strongly support him (Tillerson), and on the other hand ... the president is telling him to knock it off."
Mattis responded that the president's guidance to both him and Tillerson "has been very clearly that we would pursue the diplomatic effort," which the retired Marine Corps four-star general said includes various initiatives with China along with economic sanctions aimed at the rogue regime in Pyongyang
Mattis termed the current approach to nuclear-armed North Korea "a dynamic balance as we try to go forward with a solution." Yet he also said the U.S. needs to "ensure we have military options."
The Defense secretary said he believes Tillerson accurately stated that the U.S. "is probing for opportunities to talk with the North. All we're doing is probing; we're not talking with them."
According to Mattis, that approach to North Korea is "consistent with the president's dismay about not talking with them before the time is right." He then quickly added, "before they are willing to talk."
"So I do not see the divergence as strongly as some have interpreted it," said Mattis.
Trump tweeted Sunday, "I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man."
Last month, Trump referred to North Korea's leader as "Rocket Man on a suicide mission." Those comments were made during the president's first speech to the United Nations General Assembly.
Speaking to the Senate panel Tuesday, Mattis termed the current approach to North Korea "a dynamic balance as we try to go forward with a solution." Yet he said the U.S. needs to "ensure we have military options."
Trump "has a responsibility to ensure that we go into this with our eyes wide open," said Mattis. He noted that there's been both Republican and Democratic administrations in the past that have been disappointed in the end with diplomatic initiatives to Pyongyang.
Earlier this year, Tillerson said the U.S. under prior administrations had given more than $1.3 billion in assistance to North Korea but had little to show for it. The U.S. has been putting pressure on China, North Korea's longtime ally, to get the regime to change its behavior.
North Korean leader Kim Jong Un recently conducted the regime's sixth nuclear test and is aggressively pushing ahead with its ballistic missile development program, including test-firing intercontinental ballistic missiles some U.S. experts believe can reach at least half of the continental United States.
Also, North Korea has threatened to fire missiles toward the U.S. territory of Guam and has more recently threatened to launch a nuclear test in the open Pacific.
Tuesday's hearing of the Senate Armed Services Committee was scheduled to focus on the administration's new Afghanistan strategy but a few of the questions were about North Korea and Iran. Also speaking at the hearing was Gen. Joseph Dunford Jr., chairman of the Joint Chiefs of Staff.
Regarding Iran, Mattis told the Senate panel he believes it's best for the U.S. to stay in the Iran nuclear deal although insisted he's still supportive of efforts to review the Obama-era agreement. "If we can confirm that Iran is living by the agreement, if we can determine that this is in our best interest, then clearly we should stay with it," Mattis said Tuesday.
Meanwhile, Dunford also weighed in on Iran and said it is "not in material breach" of the international nuclear deal.
The Trump administration is facing an Oct. 15 deadline to notify Congress of Iran's compliance with the nuclear deal, the 2015 international agreement that includes the U.S. and five other world powers: Russia, China, Britain, France and Germany.
The Trump administration has certified Iran's compliance twice, but recent comments from the president suggest he may reject it this time.