President Donald Trump signaled over the weekend that he is not interested in negotiating with North Korea over its nuclear weapons and ballistic missile programs.
He said Secretary of State Rex Tillerson is "wasting his time" trying to talk to North Korean leader Kim Jong-un, after the diplomat acknowledged there was direct communication between the sides.
"The Defense Department supports fully Secretary Tillerson's efforts to find a diplomatic solution, but remains focused on defense of the United States and our allies," Mattis told a Senate Armed Services Committee hearing.
He added that Trump's guidance to both Tillerson and himself has been "very clearly" to pursue the diplomatic effort.
"I do not see the divergence as strongly as some have interpreted it," Mattis said, recalling that Tillerson had said the US is "probing" for opportunities for dialogue with the North, not looking to talk immediately.
Tensions have escalated amid a war of words between Trump and the Kim regime over Pyongyang's pursuit of a nuclear-tipped ballistic missile capable of reaching the US mainland.
Trump has said the US may have no choice but to "totally destroy" North Korea if it is forced to defend itself or its allies. Pyongyang has responded with threats to test a hydrogen bomb over the Pacific Ocean and shoot down American bombers even in international air space.
Mattis argued Trump demonstrated his intent to work diplomatically with other nations on the North Korea issue by dispatching Tillerson to China last week.
He also underscored the international community's efforts to address the North Korean threat, including through two unanimous UN Security Council resolutions since August.
Those sanctions were adopted in response to North Korea's two intercontinental ballistic missile tests in July and sixth nuclear test in September.
Separately, the Trump administration has stepped up unilateral financial sanctions on Pyongyang.
But the recalcitrance of Kim's regime may call for still tougher sanctions, said the chairman of the Joint Chiefs of Staff.
"If there was one area that has been identified by many people as maybe being the one that would most profoundly change his behavior, it would be the loss of oil," Marine Gen. Joe Dunford said at the same hearing. "We've seen in the past, when he's had a cut -- when the oil has been cut off, there's been a change in Kim Jong-un's behavior."
White House spokeswoman Sarah Sanders told reporters Monday that "now is not the time to talk."
The only conversations Washington will have with Pyongyang will be about the release of three Americans currently detained in the North, she said. (Yonhap)