Aides warned Trump not to attack North Korea's leader personally before his fiery UN address

Senior aides to President Donald Trump repeatedly warned him not to deliver a personal attack on North Korea's leader at the United Nations this week, saying insulting the young despot in such a prominent venue could irreparably escalate tensions and shut off any chance for negotiations to defuse the nuclear crisis.

Trump's derisive description of Kim Jong Un as "Rocket Man on a suicide mission" and his threat to "totally destroy" North Korea were not in a speech draft that several senior officials reviewed and vetted Monday, the day before Trump gave his first address to the U.N. General Assembly, two U.S. officials said.

Some of Trump's top aides, including national security adviser H.R. McMaster, had argued for months against making the attacks on North Korea's leader personal, warning it could backfire.

But Trump felt compelled to take a harder line.

Some advisers now worry that the escalating war of words has pushed the impasse with North Korea into a new and dangerous phase that threatens to derail the monthslong effort to squeeze Pyongyang's economy through sanctions to force Kim to the negotiating table.

A detailed CIA psychological profile of Kim, who is in his early 30s and took power in late 2011, assesses that Kim has a massive ego and reacts harshly and sometimes lethally to insults and perceived slights.

It also says that the dynastic leader - Kim is the grandson of the communist country's founder, Kim Il Sung, and son of its next leader, Kim Jong Il - views himself as inseparable from the North Korean state.

As predicted, Kim took Trump's jibes personally and especially chafed at the fact that Trump mocked him in front of 200 presidents, prime ministers, monarchs and diplomats at the U.N.

Kim volleyed insults back at Trump in an unprecedented personal statement Thursday, calling Trump "a mentally deranged U.S. dotard" and a "gangster" who had to be tamed "with fire."

Kim's foreign minister, Ri Yong Ho, threatened to respond with "the most powerful detonation," a hydrogen bomb test in the Pacific Ocean, according to South Korea's Yonhap News Agency.

Trump lobbed another broadside Friday, tweeting that Kim "is obviously a madman" who starves and kills his own people and "will be tested like never before!"

The clash may undermine Trump's other efforts on the sidelines of the General Assembly meetings.

He spent much of Thursday meeting with Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in in an effort to carve out new ways to pressure Kim to freeze or roll back his nuclear program.

On Thursday, Trump announced new U.S. sanctions against other countries, foreign businesses and individuals that do business with North Korea, a move likely to chiefly affect China, Pyongyang's largest trading partner.

John Park, a specialist on Northeast Asia at Harvard's Kennedy School, said the tit-for-tat insults have created a "new reality" and probably have shut off any chance of starting talks to freeze or roll back North Korea's nuclear program.

"If the belief centers around sanctions being the last hope to averting war and getting North Korea back to the negotiating table, it's too late," Park said.

In recent months, Pyongyang has tested its first two intercontinental ballistic missiles, conducted an underground test of what it claimed was a hydrogen bomb, and fired mid-range missiles over northern Japan.

U.S. experts assess that North Korea is six to eight months from building a nuclear warhead capable of surviving the intense heat and vibrations of an intercontinental ballistic missile capable of reaching the continental United States.

Given Kim's record of putting political rivals and dissenters to death, including members of his own family, his public statement blasting Trump makes it highly unlikely that other North Korean officials would participate in talks about ending the country's nuclear program, Park said.

"There is no one on the North Korean side who is going to entertain or pursue discussion about a diplomatic off-ramp, because that individual would be contradicting the leader, which is lethal," Park said.

Trump has returned to rhetoric he'd used during the campaign when he called Kim a "madman playing around with nukes" and a "total nut job."

But Trump also praised Kim at the time, saying during a Fox News interview last year that Kim's "gotta have something going for him, because he kept control, which is amazing for a young person to do."

In May, he said he'd be "honored" to meet Kim under the right circumstances.