It is official US policy not to protect Canada in the event of a missile attack by North Korea or any other country, a leading general has warned.

It has long been assumed that Washington would defend its northern neighbour.

However, General Pierre St-Amand, the highest-ranking Canadian officer in the North American Aerospace Defense Command (Norad), dismissed the idea during a parliamentary committee meeting in Ottawa.

“The extent of the US policy is not to defend Canada. That's the fact I can bring to the table,” he said.

This statement surprised many in Canada, with public broadcaster CBC saying it had “demolished a long-held political assumption” that the US would intervene.

Norad is a joint US and Canadian organisation “charged with ... the detection, validation and warning of attack against North America whether by aircraft, missiles, or space vehicles, through mutual support arrangements with other commands”.

Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Show all 6 1 /6 Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Photos released by North Korea show Kim Jong-un talking to subordinates next to a device thought to be the new thermonuclear weapon. There is no way of independently verifying the pictures STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb North Korea claims it has successfully tested an advanced hydrogen bomb which could be loaded onto an intercontinental ballistic missile AFP/Getty Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A diagram on the wall behind Mr Kim shows a bomb mounted inside a cone STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb North Korean leader Kim Jong-Un (C) attending a photo session with participants of the fourth conference of active secretaries of primary organisations of the youth league of the Korean People's Army (KPA) in Pyongyang STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A new stamp issued in commemoration of the successful second test launch of the "Hwasong-14" intercontinental ballistic missile KCNA via Reuters Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A new stamp issued in commemoration of the successful second test launch of the "Hwasong-14" intercontinental ballistic missile KCNA via Reuters

However, General St-Amand suggested the official policy might not necessarily be the one carried out in the event of an attack.

A decision would be made “in the heat of the moment” by the Trump administration and US military commanders, he said.

Mark Gwozdecky, assistant deputy minister for international security at Global Affairs Canada (the government department that handles diplomacy) said there had been “no direct threat to Canada” from North Korea.

“On the contrary, in recent contacts with the North Korean government, including in August when our national security adviser was in Pyongyang, the indications were they perceived Canada as a peaceful and indeed a friendly country,” he said.

However Mr Gwozdecky added that North Korea’s recent actions – which include nuclear bomb tests and firing missiles over Japan – “represent a grave threat to regional security, our friends and allies, South Korea and Japan”.