Mark Esper’s remark came as Pyongyang said they will send a “Christmas gift” if Washington did not act to ease tensions. The North Korean regime has grown frustrated after a lack of relief from sanctions despite three summits between Kim Jong-Un and Donald Trump. Mr Esper said: “I remain hopeful that we could get the process started again and remain on the diplomatic path.”
He spoke next to General Mark Milley, the chairman of the Joint Chiefs of Staff, and said the US was ready “to fight tonight” if needed.
General Milley told reporters: “Korea is one of those places in the world where we’ve always maintained high levels of readiness.
He did not comment on whether the US and allies had stepped up defence against the possibility of another nuclear test by North Korea.
Mr Milley did say: “North Korea has indicated a variety of things.
“And I think you’re aware of all those.
“So we are prepared for whatever.”
Officially assuming office yesterday, Stephen Biegun is now US Deputy Secretary of State, with Secretary of State being the American equivalent of Britain’s Foreign and Commonwealth Secretary.
He has visited Seoul, Tokyo and Beijing this week for discussions on the regional security situation.
In Seoul, Mr Biegun said the promise of a “Christmas gift” was “so hostile and negative and so unnecessary”.
He called for Pyongyang to restart discussions.
Mr Biegun insisted: “It is time for us to do our jobs.
Labour's Barry Gardiner compares Tories to North Korea dictatorship (LATEST)
Veteran NASA astronaut reveals what North Korea looks like from space (VIDEO)
How Corbyn's senior adviser expressed SUPPORT for North Korea (ANALYSIS)
“Let’s get this done.
“We are here and you know how to reach us.”
He said another missile test would be “most unhelpful in achieving lasting peace on the Korean peninsula.”
Korea was under Japanese rule until the end of the Second World War.
The USSR occupied the North and the US occupied the South after the end of the Soviet-Japanese War, with a boundary at the 38th parallel, though after a series of border clashes the North Korean regime invaded the South.
The conflict ended in a military stalemate.
Both Seoul and Pyongyang consider themselves the sole legitimate government of the entire Korean Peninsula.
Neither officially recognises the other.
In June, Trump became the first sitting US President to enter North Korea.