The NATO military alliance stands strong in its support of Ukraine and is "prepared for all eventualities," said NATO Secretary-General Jens Stoltenberg in a DW interview.

Speaking with Conflict Zone host Sarah Kelly from the Berlin Foreign Policy Forum, Stoltenberg said recent developments — Russia's partial troop mobilization, the illegal annexation of Ukrainian territory in the east and the Kremlin's "dangerous nuclear rhetoric" — represented the "biggest escalation since the war" began in late February.

"We cannot be intimidated or accept blackmailing from Russia," he said. "This nuclear rhetoric and the threats we have seen from Russia, their aim is, of course, to coerce us, to blackmail us, to stop providing support to Ukraine."

While Stoltenberg deemed the risk of nuclear attack by Russia as low, he said the impact of such an attack meant the West had to be ready. "The nuclear rhetoric coming from President Putin is dangerous, is reckless, and therefore we have to take this threat seriously."

The military alliance is preparing for all scenarios in a nuclear deterrence capabilities exercise taking place this week. The routine maneuvers, dubbed Steadfast Noon, involve 60 aircraft from 14 of the 30 NATO member countries.

Ukraine preparing for winter

As the cold winter months approach, Russia appears to be focused on damaging civilian infrastructure, and by Monday had managed to disable about a third of Ukraine's power stations.

"This demonstrates the brutality of the war… And it just also highlights the importance of NATO and NATO allies and partners that we continue to provide support to Ukraine," said Stoltenberg, adding that "we all need to do more now."

"Since we still see significant Russian presence, we need to make sure that we provide support for the long haul, as much as it takes for as long as it takes," he said.

Since the outbreak of the war in February, Stoltenberg pointed out, Ukraine's allies have mostly sent supplies by relying on their existing stockpiles. "At some stage we cannot continue to do so. So now we need also to ramp up production," he said. The allies, he added, are also preparing to supply Ukraine with military and civil winter equipment such as tents, power generators and warm clothing.

NATO defense spending on the rise

According to Stoltenberg, NATO collective defense capabilities are in the best shape they've been in a long time.

"What we have seen since 2014 is the biggest reinforcement of NATO's collective defense since the end of the Cold War," he said. "For the first time in history we have battlegroups in the eastern part of the alliance and all of this was triggered by the Russian annexation of Crimea and the control over eastern Donbas. So we were actually prepared when the invasion happened in February."

Wrapping up the interview, Stoltenberg called on Russian President Vladimir Putin to end the war. "It was President Putin that started this war, and it's President Putin who could end this war tomorrow by withdrawing his forces," he said. "If President Putin and Russia stops fighting, there will be peace."

Edited by: Martin Kuebler