The world is a much more dangerous place than it has been for a generation, according to Nato secretary general Jens Stoltenberg.
The military alliance chief, who served as the Prime Minister of Norway between 2005 and 2013, said the number of threats arising simultaneously was making the world highly unsafe.
"It is more unpredictable, and it's more difficult because we have so many challenges at the same time," he said in an exclusive interview with the Guardian.
"We have proliferation of weapons of mass destruction in North Korea, we have terrorists, instability, and we have a more assertive Russia. It is a more dangerous world."
Stoltenberg's comments come amid the escalating nuclear crisis in the Korean peninsula, where the South Korean government has deployed the US Thaad missile defence system in response to the growing threat poised by North Korea's military activity.
Over the last couple of weeks, Pyongyang has fired a ballistic missile over Japan, tested a possible thermonuclear device and threatened to launch an attack against the US Pacific territory of Guam.
On the other side of the Pacific, US President Donald Trump has threatened to unleash "fire and fury" on North Korea, should Pyongyang make further threats. On Thursday (7 September), Trump said Washington was ramping up military power.
"It's been tens of billions of dollars more in investment," he said.
"And each day new equipment is delivered – new and beautiful equipment, the best in the world, the best anywhere in the world, by far.
"Hopefully we're not going to have to use it on North Korea. If we do use it on North Korea, it will be a very sad day for North Korea."
Asked whether a military solution could be on the cards to solve the crisis on the Korean peninsula, the Nato secretary general said: "I think the important thing now is to look into how we can create a situation where we can find a political solution to the crisis.
"At the same time I fully understand and support the military message that has been implemented in the region by South Korea and to some extent Japan, as they have the right to defend themselves.
"They have a right to respond when they see these very aggressive actions. I also support the presence of US troops and capabilities in Korea."
Meanwhile, for a six-day period starting from next Thursday approximately 100,000 Russian troops will be deployed on the country's border with the European Union. Russian and Belarusian troops, as well as security personnel and civilian officials will take part in the exercise, which is understood to be the biggest of its kind Moscow has conducted since the Cold War.
The troops will be active in the area around the Baltic Sea, western Russia, Belarus and the Russian exclave of Kaliningrad.
"Russia has said it [the number of troops deployed] is below 13,000," Stoltenberg said.
"They briefed that on the Nato-Russia council a few weeks ago. That was useful but at the same time we have seen when Russia says that an exercise has less than 13,000 troops that's not always the case.
"We have seen that in Zapad 2009 and 2013 – the two previous Zapad exercises. There were many more troops participating."