He then came out in support of Kyiv over its request to use Western weapons on targets inside Russia.
And now ahead of the next Nato summit, he has tabled proposals for the alliance to play a greater role in the West’s support for Ukraine.
About 99 per cent of the weapons deliveries to Kyiv are done so by Nato allies, he says.
His new Nato security assistance and training for Ukraine scheme – downgraded from the Mission to Ukraine because of German fears over Russian escalation – will have 700 Nato personnel stationed at its headquarters in Wiesbaden, Germany, take over the bulk of the coordination of aid from the Americans.
Mr Stoltenberg said, cautious not to mention the looming prospect of the election of Mr Trump: “This is a proposal which is about making the support for Ukraine more robust, more long term, more predictable, and that’s something which is important regardless of the outcome of the elections in the United States.
“We saw the gaps and delays this winter, where several allies were not able to deliver the support they had promised. We have to minimise the risk of something like that happening again.”
He added: “If we have a Nato support, security assistance and training effort combined with a long-term financial pledge, I think we will give a much stronger message to Moscow that President Putin cannot wait us out.”
But it is not just the US where support for Ukraine could be flipped on its head.
Last week, France’s Emmanuel Macron called snap elections after his party was defeated in the EU voting by far-Right leader Marine Le Pen, who has previously enjoyed close ties with Putin and called for closer relations between Nato and Moscow.
Mr Stoltenberg said: “I believe it is in the interest of all allies, including France and others, to keep Nato strong because we live in a more dangerous world.
“In a more dangerous world, it’s even more important that North America and Europe stand together.
“Then, of course, we are 32 democracies and it’s part of democracies that we have different parties, different views, different opinions, but experience over these decades is that despite all these differences, there has always been strong support for Nato.”
And in a call for them to continue arming Ukraine, he concluded: “I strongly believe that if Putin prevails in Ukraine, we will become more vulnerable, and then we will need to invest even more in our defence.”