Trump addresses the 72nd United Nations General Assembly at UN headquarters in New York REUTERS/Eduardo Munoz

US President Donald Trump has issued a fresh warning to North Korea via his favourite social media platform, Twitter. He threatened the country's leaders "won't be around much longer" if Pyongyang presses ahead with its constant threats.

Trump's latest tweet marks another notch in the sharp escalation of the war of words, which has been occurring between the two countries in recent weeks. The American leader's response comes shortly after North Korea's foreign minister made his speech at the UN.

In a late evening tweet on Saturday (23 September), Trump wrote: "Just heard Foreign Minister of North Korea speak at the UN. If he echoes thoughts of Little Rocket Man, they won't be around much longer!"

Trump's threat comes just hours after he posted a similar message on Iran. He accused Iran, which recently conducted a ballistic missile test, of working with North Korea in its weapons programme without offering many details.

"Iran just test-fired a ballistic missile capable of reaching Israel. They are also working with North Korea. Not much of an agreement we have," said the American president, who used his earlier address at the UN General Assembly to target both North Korea and Iran among other nations.

North Korean Foreign Minister Ri Yong-ho had earlier said a rocket attack on the US mainland is "inevitable" given the constant insults emerging out of Washington.

Through such a prolonged and arduous struggle, now we are finally only a few steps away from the final gate of completion of the state nuclear force," Ri told the UN gathering.

"It is only a forlorn hope to consider any chance that the DPRK [North Korea] would be shaken an inch or change its stance due to the harsher sanctions by the hostile forces," he added.