North Korea probably won’t be happy with Bob Woodward’s explosive new book about the Trump presidency — and it could hurt the administration’s effort to convince North Korea to give up its nuclear weapons.

In an excerpt published on Tuesday, Woodward recounts an exchange between President Donald Trump and Secretary of Defense Jim Mattis. In it, Trump calls for killing Syrian President Bashar al-Assad after his regime murdered over 80 people with chemical weapons in April 2017.

“Let’s fucking kill him! Let’s go in. Let’s kill the fucking lot of them,” Trump told Mattis, referring to Assad and his forces.

The president never authorized the assassination, instead choosing a more limited bombing of a Syrian airbase, and both Trump and Mattis deny that conversation ever happened.

But there’s more: Woodward also reports that Trump asked Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, to come up with a plan to preemptively attack North Korea.

That’s consistent with previous reporting indicating the administration considered a so-called “bloody nose” strike, meant to compel Pyongyang to give up its nuclear weapons.

Experts worry that these two revelations could hurt America’s nuclear negotiations with North Korea by convincing leader Kim Jong Un that Trump would be willing to order an assassination strike against him — which is a really strong reason for Kim to hold onto his nuclear bombs and missiles.

Kim Jong Un will never unilaterally disarm. And this is why. We can get hung up on sequencing and details but fundamentally this is the problem. pic.twitter.com/0SyUlKqNCx — Vipin Narang (@NarangVipin) September 4, 2018

Kim, like his father and grandfather before him, considers nukes to be the greatest deterrent to a US-led attack on North Korea, and especially attacks meant to topple the leadership.

Trump and Mattis’s Syria conversation and the preemptive strike option that Trump requested play right into North Korean fears of what America might do. As North Korea nuclear expert Vipin Narang of MIT points out above, “Kim Jong Un will never unilaterally disarm” because he wants to safeguard against such an attack.

The Trump administration’s job in ongoing nuclear talks with North Korea is to convince it that an attack will never come. Trump’s reported comments make that job much harder.