Pentagon chief Jim Mattis said Tuesday his department "supports fully" Secretary of State Rex Tillerson's effort to find a diplomatic solution to the North Korea nuclear stand-off.
Defense Secretary Mattis was speaking two days after President Donald Trump appeared to undermine his top diplomat by saying he was "wasting his time" by talking to Kim Jong-Un's regime.
State Department officials insist Trump was not criticizing Tillerson, but pressuring Kim Jong-Un's regime to agree to discuss its disarmament while a diplomatic option remains on the table.
Mattis, in testimony to the House Armed Services Committee, said the Pentagon stands four square behind the strategy -- and singled out Tillerson for support.
"The international community... is focused on the destabilizing threat posed by North Korea and Kim Jong-Un's relentless pursuit of nuclear and ballistic missile capabilities," he said.
"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."
Tillerson has explained the strategy as one of using United Nations and US sanctions and diplomatic pressure to convince Kim of his isolation and force him to negotiate nuclear disarmament.
US officials insist publicly that they have military options to counter the threat from Pyongyang if this fails, but admit privately that they are risky.
So it was hard to square Tillerson's diplomatic push with the Trump tweets that greeted him Sunday as he flew back from meeting Chinese leader in Beijing.
"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man," Trump wrote, using his dismissive nickname for Kim.
"Save your energy Rex, we'll do what has to be done!" he added, apparently suggesting that some kind of non-diplomatic option was back on the table.
"Being nice to Rocket Man hasn't worked in 25 years, why would it work now? Clinton failed, Bush failed, and Obama failed. I won't fail."
Kim is 33 years old and came to office in 2011, but Trump appears to have been referring to previous US efforts to deal with his father and grandfather.
While in China, Tillerson had told reporters that he was "probing" whether the North is ready for talks on the denuclearization of the Korean peninsula.
"So stay tuned," he added.
"We have lines of communications to Pyongyang. We're not in a dark situation, a blackout. We have a couple, three channels open to Pyongyang. We can talk to them. We do talk to them."
This revelation appears to have triggered Trump's tweeted response -- which in turn sparked fresh rumors of tensions between the president and his top diplomat.