Vice President Mike Pence said "all options are on the table" as North Korea continues to develop its nuclear-weapons and ballistic-missile programs, during a speech Wednesday aboard the aircraft carrier USS Ronald Reagan.
North Korea's Ambassador to the United Nations has warned nuclear war may break out at any moment, accusing the USA of turning the Korean Peninsula into the "world's biggest hotspot".
"That deployment of such a defence system reflects a strong defence and security alliance between South Korea and the USA and is a direct response to the threat posed by North Korea", she said.
Tensions have risen as Trump takes a hard rhetorical line with Kim Jong Un, who has rebuffed admonitions from China and proceeded with nuclear and missile programmes seen by Washington as a direct threat.
Past administrations, though, have failed to stop, let alone slow down, North Korea's nuclear program and ballistic missile developments.
Things are heating up on the Korean peninsula, you may have heard.
Trump himself appeared to reinforce the stern US message at the White House, replying "Gotta behave" when a CNN reporter asked what message he had for North Korean leader Kim Jong Un.
In a 2010 statement sent to China, North Korea's forestry ministry said the trucks were bought to transport timber, according to the United Nations report.
The vice-president referenced the recent illegal United States air strikes against Syria and added pointedly: "North Korea would do well not to test [President Donald Trump's] resolve".
Speaking alongside South Korea's acting President Hwang Kyo-ahn, Pence said the previous US administration had observed a policy of "strategic patience", but this was now over.
Behind the heated rhetoric, in fact, Trump's strategy in the region looks somewhat similar to predecessor Barack Obama's - albeit with the added unpredictability of a new president who has shown he's willing to use force.
He said that with the action on Syria, Trump "made sure that members of Congress were notified of his action in a very, very short amount of time".
China says the crisis is between the United States and North Korea.
Pence on Monday had traveled to the tense zone dividing the two Koreas, where he warned North Korea's leaders that after years of testing the USA and South Korea with its nuclear ambitions, "the era of strategic patience is over".
While the North did not conduct a nuclear test, the specter of a potential test and an escalated US response has trailed Pence as he undertakes his Asian tour.
He was asked to respond to Trump's suggestion that North Korea should "behave", but declined. "If they were unwilling to help us with this, it's going to make other aspects of our bilateral relationship potentially more contentious".
Pence declared that North Korea had tested the world's patience for two decades and "answered our overtures with wilful deception, broken promises and nuclear and missile tests".
The Pyongyang regime points to instances of U.S. aggression such as the Syrian air strikes, the invasion of Iraq and the bombardment of Libya that handed the country to Islamist extremists as reasons why it is developing nuclear weapons in order to defend itself.
The acting president, in addition, called the 1960 civil uprising a starting point for a free democracy to take root in South Korea, stressing the need to uphold its spirits to overcome a series of national challenges.
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