WASHINGTON – President Donald Trump's former national security adviser John Bolton slammed Trump as "not fit for office" and said he lacked "the competence" to be president in an excerpt from a television interview released Thursday morning. 

Asked about Trump's fitness for office, Bolton told ABC News, "I don't think he's fit for office. I don't think he has the competence to carry out the job."

"There really isn't any guiding principle that I was able to discern other than what's good for Donald Trump's re-election," he said. 

Bolton's book on his time in the White House, which is set for release June 23, alleges the president s consumed with re-election concerns and calls the president's foreign policy "erratic," according to excerpts reported by media outlets. 

"I think he was so focused on re-election that longer-term consideration fell by the wayside," Bolton said to ABC News of Trump's approach to foreign policy. 

Bolton called himself "sick at heart over Trump's zeal to meet with (North Korean leader) Kim Jong Un." 

"There was considerable emphasis on the photo opportunity and the press reaction to it and little or no focus on what such meetings did for the bargaining position of the United States," Bolton said.

In "The Room Where it Happened: A White House Memoir," Bolton writes that Trump asked China's President Xi Jinping to increase the country's purchase of American-grown farm products because aiding farmers would help him in the presidential race, according to an excerpt in the Wall Street Journal. The requests came during trade negotiations at the 2018 G-20 summit in Argentina and again in June 2019 at the summit in Japan.

"In exchange (for concessions on tariff rates), Trump asked merely for some increases in Chinese farm-product purchases, to help with the crucial farm-state vote," Bolton writes of the Argentina meeting. "If that could be agreed, all the U.S. tariffs would be reduced. It was breathtaking."

And in Japan, Trump "turned the conversation to the coming U.S. presidential election, alluding to China’s economic capability and pleading with Xi to ensure he’d win," Bolton writes.

Bolton left the White House in September 2019. He said he resigned, but Trump said he fired his national security adviser.  

In a Wednesday interview with the Wall Street Journal, Trump pushed back on Bolton's claims, calling Bolton a "liar" and adding, "Everyone in the White House hated John."

The Trump administration has sued to block Bolton from publishing his book and asked a federal judge Wednesday night for an emergency order blocking its publication. 

Author, but he's no patriot:' Lawmakers react to Bolton's new book on Trump