Donald Trump’s hawkish new choice for national security adviser has cast doubt on upcoming talks with North Korea, a Republican senator said.

“He has a very healthy scepticism of North Korea”, Lindsey Graham, a South Carolina Republican and administration ally, said of newly elevated adviser John Bolton in an appearance on Fox News Sunday.

“I had dinner with Bolton a couple of nights ago. His big fear is that they’re just buying time”, Mr Graham said. “He sees these negotiations as a way of buying time”.

Mr Bolton's ascendance comes at a critical time for the world’s effort to contain North Korean military ambitions, with a rare diplomatic window offering glimmers of a breakthrough.

The president has agreed to North Korean leader Kim Jong-un’s proposal that the two heads of state meet face-to-face, an unprecedented move that has fanned hopes of a peaceful resolution to mounting tensions on the Korean peninsula. Mr Kim has said he is committed to “denuclearisation”, according to a South Korean envoy who detailed the overture.

But wariness about the sincerity of North Korea’s intentions abounds. The United States has continued to maintain pressure on the regime, backing new sanctions on companies accused of doing business with Pyongyang and this weekend joining South Korean troops in holding military exercises.

US/South Korea joint exercise Operation Pacific Reach Show all 10 1 /10 US/South Korea joint exercise Operation Pacific Reach US/South Korea joint exercise Operation Pacific Reach US Marine soldiers patrol during the US-South Korea joint Exercise Operation Pacific Reach in Pohang, South Korea. North Korea is vowing tough counteraction to any military moves that might follow the US move to send the USS Carl Vinson aircraft carrier and its battle group to waters off the Korean Peninsula AP US/South Korea joint exercise Operation Pacific Reach South Korean soldiers take part in the Operation Pacific Reach joint logistic exercise in Pohang, South Korea Reuters US/South Korea joint exercise Operation Pacific Reach North Korea is vowing tough counteraction to any military moves that might follow the US move to send the USS Carl Vinson aircraft carrier and its battle group to waters off the Korean Peninsula AP US/South Korea joint exercise Operation Pacific Reach South Korean marine soldiers stand guard during the US-South Korea joint Exercise Operation Pacific Reach in Pohang, South Korea AP US/South Korea joint exercise Operation Pacific Reach A US Marine takes part in Operation Pacific Reach joint logistic exercise in Pohang, South Korea Reuters US/South Korea joint exercise Operation Pacific Reach A US Marine takes a position during a Combined Joint Logistics Over-the-Shore (CJLOTS) exercise as part of a joint defence exercise at a beach in Pohang Getty Images US/South Korea joint exercise Operation Pacific Reach South Korea and the United States kicked off a combined distribution exercise focused on integrating the two sides alliance logistics capabilities, in Pohang, 260 kms southeast of Seoul Getty Images US/South Korea joint exercise Operation Pacific Reach South Korea and the United States kicked off a combined distribution exercise focused on integrating the two sides alliance logistics capabilities Getty Images US/South Korea joint exercise Operation Pacific Reach A US Marine walks past a military vehicle during a Combined Joint Logistics Over-the-Shore (CJLOTS) exercise as part of a joint defence exercise in Pohang Getty Images US/South Korea joint exercise Operation Pacific Reach US Marines gather at a beach during a Combined Joint Logistics Over-the-Shore (CJLOTS) exercise as part of a joint defence exercise in Pohang, 260 kms southeast of Seoul, South Korea Getty Images

In selecting Mr Bolton to be his top security aide, Mr Trump ensured a pro-military intervention voice will be prominent in his administration.

A vocal supporter of the American invasion of Iraq, Mr Bolton has advocated preemptive military strikes on Iran and North Korea.

He has long been leery of diplomacy’s efficacy, famously saying that if the United Nations headquarters “lost 10 stories, it wouldn't make a bit of difference”. He has warned in recent months that diplomatic efforts to quell North Korean aggression are futile.

“I think the only diplomatic option left is to end the regime in North Korea by effectively having the South take it over”, Mr Bolton told Fox News last year.

Newly appointed US National Security Advisor John Bolton 'wasn't expecting' Trump to make the announcement with a tweet

He will now be advising a president who has shown few compunctions about threatening foes with a military strike. As North Korea tested intercontinental ballistic missiles and a hydrogen bomb, Mr Trump and his surrogates repeatedly warned America could respond with overwhelming force.

“The US has great strength and patience,” Mr Trump said in his first speech to the United Nations, but “if it is forced to defend ourselves or our allies, we will have no choice but to totally destroy North Korea.”

The escalating martial rhetoric has given way to cautious expressions of optimism amid North Korea’s latest overture. Pyongyang’s offer of talks with the US came with a pledge to suspend weapons tests, a South Korean envoy said.