Ex-US National Security Adviser John Bolton on Monday criticized President Donald Trump’s North Korea policy and warned that the Asian Country posed an “imminent” threat.

Taking to Twitter, Bolton said, “The risk to US forces & our allies is imminent & more effective policy is required before NK has the technology to threaten the American homeland”.

The erstwhile advisor, a longtime hawk on North Korea, was openly sceptical of the 2018 summit between Trump and North Korean leader Kim Jong Un and encouraged the US president to be cautious.

The denuclearization process has been largely deadlocked since the collapse of a second summit in Hanoi at the start of this year. North Korea promised an ominous “Christmas gift” earlier this month if Washington does not give ground by the end of December.

Bolton also criticized Trump for saying the North Korean short-range missile tests don’t bother him.

“When the president says, ‘Well, I’m not worried about short-range missiles,’ he’s saying, ‘I’m not worried about the potential risk to American troops deployed in the region or our treaty allies, South Korea and Japan,'” he charged.

Earlier in October, Bolton had warned that President Donald Trump’s personal attorney Rudy Giuliani, who has emerged as the point man in the president’s alleged drive to pressure Ukraine to dig up dirt on Democratic presidential hopeful Joe Biden, is “a hand grenade who’s going to blow everyone up,” his aide Fiona Hill told lawmakers.

Earlier in September, President Trump fired Bolton, who was known for his hardline stances on Washington’s archenemies, particularly Iran, North Korea and Venezuela. He was replaced by Robert C O’Brien.