White House: Trump puts North Korea on notice

"I think he has been very clear that he will not tolerate some of those actions by North Korea," Spicer said at a regular briefing, declining to elaborate how Trump plans to solve the problem on his own without Chinese help.

"The president is not one who's going to go out there and telegraph his response. I think he keeps all options on the table, he keeps his cards close to the vest. And as he showed last week with respect to Syria, when the president's willing to act, it's going to be decisive and proportional to make it very clear what the position of the United States is," Spicer said.

Spicer also said Trump has made clear that the North's behavior and actions with respect to the missile launches are "not tolerable."

"The last thing we want to see is a nuclear North Korea that threatens the coast of the United States or, for that matter, you know, any other country and any other set of human beings. So we need stability in that region and I think he has put them clearly on notice," he said.

The US has sent an aircraft carrier strike group led by USS Carl Vinson toward the Korean Peninsula, rather than executing previously planned port visits to Australia, in a show of force designed to warn the North against additional provocations.

Secretary of Defense Jim Mattis said the decision was the "most prudent" at this time.

"She operates freely up and down the Pacific and she is just on her way up there because that's what we thought was the most prudent to have at this time. There is not a specific demand signal or specific reason why we're sending her up there," Mattis said during a briefing at the Pentagon.

Tensions on the peninsula have risen amid speculation that North Korea may conduct its sixth nuclear test or carry out a threatened test of an intercontinental ballistic missile capable of reaching the US around its key anniversaries in April.

In Tuesday's tweets, Trump also said that he told Chinese President Xi Jinping that "a trade deal with the US will be far better for them if they solve the North Korean problem."

Trump has long said North Korea is China's problem to fix, criticizing Beijing for refusing to use its leverage as the main provider of food and energy for the impoverished North to bring the recalcitrant regime under control.

China has been reluctant to use its leverage for fear that pushing the regime too hard could result in instability in the North and even its collapse, which could lead to the emergence of a pro-US nation on its border. (Yonhap)