North Korea has said that firing its rockets at mainland United States was “inevitable” after US President Donald Trump called Pyongyang’s leader “rocket man”, in a further escalation of rhetoric between the two countries over the North’s nuclear weapons and ballistic missile programme. North Korean Foreign Minister Ri Yong-ho’s remarks on Saturday before the United Nations General Assembly came hours after US Air Force B-1B Lancer bombers escorted by fighter jets flew in international airspace over waters east of North Korea in a show of force the Pentagon said showed the range of military options available to Trump. Ri’s speech capped a week of escalating rhetoric between Washington and Pyongyang, with Trump and Kim Jong-un trading insults. Trump called the North Korean leader a “madman” on Friday, a day after Kim dubbed him a “mentally deranged US dotard”. On Saturday, the insults continued with Ri calling Trump “a mentally deranged person full of megalomania and complacency” who is trying to turn the UN into a “gangsters’ nest”. Ri said Trump himself was on a “suicide mission” after the US president said Kim was on such a mission. He warned of “merciless pre-emptive action” if there was any sign of a US military attack. “‘President Evil’ is holding the seat of the US president,” Ri said, warning that Pyongyang was ready to defend itself if America showed any sign of conducting a “decapitating operation on our headquarters or military attack against our country”. “Now we are finally only a few steps away from the final gate of completion of the state nuclear force,” Ri told the annual gathering of world leaders. China bans North Korean textile imports, to squeeze oil supply in line with UN sanctions on reclusive state He said sanctions would have no effect on Pyongyang’s resolve to develop its nuclear weapons, with the ultimate goal being “balance of power with the US”. Trump announced new US sanctions on Thursday that he said allow targeting of companies and institutions that finance and facilitate trade with North Korea. Earlier this month the UN Security Council unanimously adopted its ninth round of sanctions on Pyongyang to counter its nuclear and ballistic missiles programmes. The US bombers’ flight was the farthest north of the demilitarised zone separating North and South Korea that any US fighter jet or bomber has flown in the 21st century, the Pentagon said. “This mission is a demonstration of US resolve and a clear message that the President has many military options to defeat any threat,” said Pentagon spokeswoman Dana White. “We are prepared to use the full range of military capabilities to defend the US homeland and our allies.” The Pentagon said the B-1B bombers came from Guam and the US Air Force F-15C Eagle fighter escorts came from Okinawa, Japan. It said the operation showed the seriousness with which it took North Korea’s “reckless behaviour”. No sound wave, ‘it was natural’: Chinese, South Korean monitors conclude North’s quake was not nuclear North Korea has launched dozens of missiles this year, several flying over Japan, as it accelerates its programme aimed at enabling it to target the US with a nuclear-tipped missile. Pyongyang conducted its sixth and largest nuclear test on September 3 and has threatened to test a hydrogen bomb over the Pacific. Tensions have continued to rise around the Korean Peninsula since Pyongyang carried out its sixth nuclear test, prompting a new round of UN sanctions. North Korea’s nuclear tests have so far all been underground, and experts say an atmospheric test, which would be the first since one by China in 1980, would be proof of the success of its weapons programme. The United States and South Korea are technically still at war with North Korea because the 1950-53 Korean conflict ended with a truce and not a peace treaty. The North accuses the United States, which has 28,500 troops in South Korea, of planning to invade and regularly threatens to destroy it and its Asian allies.