Guterres stressed "the importance of maintaining the unity of the international community in addressing this serious challenge", in a reference to US-Sino differences.
North Korea had immediately hailed the launch and the missile's nearly 40-minute flight as its first successful test of an ICBM, but it took almost a full 24 hours for analysis of missile data to bear that out.
North Korea's possession of an ICBM - something that Trump has vowed "won't happen" - would force a fundamental recalculation of the strategic threat posed by the isolated, impoverished state.
Prime Minister Theresa May's official spokesman said that the UK stood 'alongside' the US and other allies in confronting the threat poses by North Korea.
Donald Trump and Vladimir Putin are also expected to address growing North Korean provocations at their meeting on the sidelines of the G20 summit in Hamburg. "Does this guy have anything better to do with his life?" he tweeted late Monday, presumably referring to North Korean leader Kim Jong Un. The U.S. and South Korea had initially said the projectile was an intermediate range ballistic missile. Perhaps China will put a heavy move on North Korea and end this nonsense once and for all!'
Even direct talks with the north are unlikely to result in a nuclear free North Korea. That's enough to put Alaska within range.
If the North Korean claim is true, it means that the country has made a further step in readying for the combat deployment of this type of long-range missile, which could potentially deliver a nuclear warhead to the U.S. mainland.
"We should be concerned that it's an ICBM".