US President Donald Trump's highly-combative remarks against North Korea and its leader at the United Nations will only harden Pyongyang's resolve to continue developing its nuclear programme, analysts have warned.

Using what was described as "unprecedented" language, Trump made his debut address at the UN General Assembly (UNGA) on Tuesday.

In a wide-ranging 45-minute speech, the most anticipated foreign policy address of his tenure, Trump vowed that the US would "totally destroy" North Korea if it is forced to defend itself or its allies.

He also mocked Kim Jong-un, North Korea's leader, saying: "Rocket Man is on a suicide mission for himself and for his regime. The United States is ready, willing and able, but hopefully, this will not be necessary."

The sharp escalation in rhetoric came weeks after Trump warned that North Korea would be met with "fire and fury like the world had never seen" if it continues expanding its nuclear programme.

"I expected him to talk tough and strong - but I did not expect him to talk quite that tough and quite that strongly," said Donald Kirk, a journalist and author of several books on Korea.

He said Trump's remarks made the prospect of negotiations extremely unlikely.

"North Koreans are not going to back down - if anything they are going to increase the tempo of their programme," Kirk told Al Jazeera from South Korea's capital, Seoul. "I think we can forget about North Korea saying, 'let's go to negotiations.'"

Kirk also said he expected that Trump's fiery approach would not be adopted by other leaders who are otherwise highly critical of North Korea's actions.

"We are in for some quite interesting questions here, and a lot of it is not going to be favourable to Trump," he said. "I get the general impression that tensions will increase and the line is drawn ever deeper."

'Neoconservative line'

Mark Farha, assistant professor of international relations at the Doha Institute, said that Trump had - once again - embraced an interventionist foreign policy.

READ MORE: UN chief warns against war with North Korea

"He did so gradually in the speech; in the beginning, he began in a more conciliatory manner, and towards the end, he adopted squarely a neoconservative line of regime change and war in fact," Farha told Al Jazeera.

"He is trying to square the circle, because ... if you had a poll [in the US] 75 percent of people would be against escalation against Iran and North Korea, but here is Trump harking back to the neoconservatives."

'Steps towards undermining Iran'

In his speech, Trump also attacked Iran, accusing it of being a "rogue state and a murderous regime". He said the US could not abide by an agreement if it provided cover for the construction of a nuclear programme.

Sultan Barakat, director at the Center for Conflict and Humanitarian Studies at the Doha Institute, also said that Trump's rhetoric had raised the stakes.

"North Korea now has the script and the excuse to why they need the [nuclear] programme," he told Al Jazeera. "If they haven't got one they need to work very quickly to develop one if they have that direct threat."

Barakat noted, however, that Trump's comments about Iran were more worrisome.

"With the current circumstances and the alliances he is building with Saudi Arabia, Israel and other nations, I fear there is more chance of him taking some further steps towards undermining Iran than North Korea," said.

Trump has to certify in mid-October whether he believes Iran is abiding by a historic seven-nation agreement signed in 2015.

Al Jazeera's James Bays, reporting from the UN headquarters in New York, said Trump's comments on Iran were nothing new, as he has made it clear time and again that he is against the pact.

"Yet, saying it in this setting, in front of world leaders, and calling the deal the worst and most one-sided transaction in US history and an embarrassment to the US, I think that really makes it hard now for Trump not to de-certify the deal and pull out of it - and that's just what all the other players in the international community don't want," he said.