US Defense Secretary James Mattis has warned Pyongyang that any nuclear attack by N. Korea would trigger an "effective" response. But how is China looking at the Trump administration's aggressive stance towards its ally?
The United States is planning to use joint military exercises with South Korea in March as a show of force to both Pyongyang and Beijing that President Donald Trump intends to follow through on his vows to be firm with the enemies of America.
There were indications that the US military presence will be larger than in previous years for the regularly scheduled exercises, even before new US Defense Secretary James Mattis arrived in Seoul on Thursday to deliver the blunt message that Washington remains committed to protecting its South Korean ally.
The USS Carl Vinson supercarrier has already arrived in the western Pacific with its supporting fleet after departing from San Diego on January 5. The US Air Force has also announced that an additional 12 F-16 Fighting Falcon aircraft are to be deployed to Osan Air Base before the end of February.
There are also suggestions that the exercises may include strategic bombers.
On Wednesday, Mattis and his South Korean counterpart, Han Min-goo, reaffirmed in a telephone conversation that they will push ahead with plans to deploy a battery of the US Army's Terminal High Altitude Area Defense (THAAD) anti-missile system. The plan has attracted fierce criticism from China, which claims that it threatens to unbalance regional security.
Mattis emphasized once again during his visit to Seoul that THAAD is solely designed to protect South Korea from North Korean ballistic missiles, but Beijing is unlikely to be mollified.
"This is a gesture by the Trump administration to demonstrate that it is committed to the security of its allies in Asia and it will be particularly welcomed in South Korea, given that Trump has sowed so many doubts during the campaign about just how committed he was to continuing security alliances with South Korea and Japan," said Jeff Kingston, director of Asian Studies at the Japan campus of Temple University.
"But this will, of course, significantly ratchet up tensions with South Korea's immediate neighbor, which, we must remember, is on the brink of developing an intercontinental ballistic missile capability," he told DW.
"It seems to me that the policy of strategic patience that was exercised by the last US government may be over, and that the reaction from North Korea is going to be harshly negative."
In his New Year's address to the nation, North Korean leader Kim Jong-un stated that his military has perfected an ICBM and is ready to use it "at any time." Given that there have been no successful tests of the weapon, experts are unsure how accurate Kim's boast is - although they agree that separate tests of nuclear warheads and long-range missiles demonstrate that his scientists are edging ever-closer to giving North Korea a nuclear missile capable of striking targets in the continental US.
Trump famously Tweeted "It won't happen" - but Kingston believes it is dangerous to "draw red lines" because the president is backing himself into a corner. What happens, he asks, if Kim does carry out an ICBM test launch? Will Trump feel that his power has been challenged and that he has no choice but to retaliate, leading to a rapid escalation in responses?
Stephen Nagy, an associate professor of international relations at Tokyo's International Christian University, says North Korea's development of an ICBM or submarine-launched ballistic missiles are a "game-changer" - but that instead of a stepped-up response to North Korea, Trump's reactions are in line with the latter days of Barack Obama's presidency.
"By escalating the forces in these military exercises, Washington is making a clear message to North Korea that it will not be tolerated, and I believe that Obama would have done the same," he said.
There is evidence to support that belief, with Obama ordering US aircraft to overfly South Korean airspace after the North's SLBM test in October and using targeting technology to simulate a strike on key targets in North Korea.
"That was a very serious message designed to make Pyongyang think twice," Nagy said. "And I don't think that Trump's approach is very different from that or out of line."
And he does not believe that it will come down to a question of which leader blinks first.
"The North Korean regime sees its nuclear weapons as being a guarantee of their survival and it is sufficient that they are able to continue to develop the technology, but they also serve to legitimize the regime and, potentially, as a bargaining chip," he added.
And while tensions on the Korean Peninsula will inevitably rise in the immediate future, it is clear that Japan and South Korea will welcome Washington's renewed commitment to their security - whether that be threatened by North Korean nuclear weapons or China's expansionist policies in the region.