Secretary of State Rex Tillerson backs "the wrong policy" on North Korea and is not in agreement with President Trump, according to former ambassador John Bolton.

Bolton took aim at Tillerson hours after Trump delivered a speech at the United Nations General Assembly that the former Bush administration diplomat hailed as the best of Trump's tenure in office. He suggested that Trump's national security team might not want to follow through on the speech and make a credible military threat to deter North Korea's nuclear weapons development.

"The president in the speech today... particularly on Iran and North Korea, could not have been more clear," Bolton said at a conference hosted by United Against Nuclear Iran. "The issue is whether the rest of his government feels the same way."

Tillerson, Bolton noted, had said the United States has imposed economic sanctions on North Korea in order to induce a "constructive, productive dialogue" with the regime. But Bolton dismissed that as a repetition of failed policies.

"Now, we've had constructive dialogue with North Korea for 25 years; it doesn't work," Bolton said. "That's the wrong policy."

Bolton said he doubts that any sanctions would succeed in changing North Korea's behavior.

"Sanctions, I think, can work in certain limited circumstances, but they have certainly not worked in the case of Iran and North Korea for 25 years," Bolton said. "There's no prospect they will work in year 26."

Bolton was previously a contender to lead the State Department, or at least have a senior post at Foggy Bottom, but he has been on the outs with Trump's team of late. Most notably, he published a memo about abandoning the Iran deal that he said Trump's advisors had prevented him from submitting to the president.

"Although he was once kind enough to tell me ‘come in and see me at any time,' those days are now over," Bolton wrote in National Review. "If the president is never to see this option, so be it. But let it never be said that the option didn't exist."

Bolton touted Japanese Prime Minister Shinzo Abe's affirmation, in a New York Times op-ed this week, "that all options are on the table" when it comes to North Korea. He said that showed that Abe would support the United States in an attack in North Korea.

"If there were any chance of avoiding military hostilities, it would be because that's what North Korea and China felt certain would be about to happen," he said. "So we'll see over the next several months."