NATO Secretary-General Mark Rutte has said that this is "not the time to go it alone, not for Europe or America" and that the current global security challenges are "too big to face on our own".
"When it comes to keeping Europe and North America safe, there is no alternative to NATO," he said.
Mr Rutte made the remarks during a speech on transatlantic security this afternoon at the Warsaw School of Economics.
"Nothing can replace America's nuclear umbrella, the ultimate guarantor of our security," he said in front of a packed auditorium of professors, students and analysts from Polish think tanks.
The NATO chief’s remarks come after weeks of uncertainty about the future of the transatlantic partnership, after the Trump administration reengaged with Russia to start peace talks on the war in Ukraine, bypassing the involvement of European governments in the process.
Mr Rutte said he was convinced the US remained committed to NATO and Article 5 of the alliance’s treaty which says that an attack on one member is an attack on all.
Addressing current US-brokered efforts to bring about a ceasefire in the three-year Russia-Ukraine war, Mr Rutte said: "I am glad that President Trump broke the deadlock because we feel that it was necessary and positive that peace talks are being conducted now under his leadership.
"The Americans and all of us, we always been very clear that we need to bring Ukraine a durable and lasting peace. Vladimir Vladimirovich Putin should never try again to attack Ukraine."
Mr Rutte said it was important that discussions are now taking place between European countries on how to "potentially help maintain peace in Ukraine".
In relation Russia’s maximalist demands in order for the war to end, including the withdrawal of NATO multinational battalions from across Eastern Europe, Mr Rutte said: "Putin can put whatever he wants on the table but he has absolutely no say in how we organise ourselves within the 32-member alliance".
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He said that Russia’s latest missile technology meant that all NATO members were effectively on the alliance’s "eastern flank".
The NATO chief said that, even after the war in Ukraine ends, "Russia will remain a significant and direct threat to our security".
Russia’s president, said Mr Rutte, has "not given up his condition to reshape the global security order," adding that China was also expanding its military and nuclear force "with no limits or transparency".
"Putin has to know that when he will try to get a square kilometre of Estonia or Poland or Slovakia, or Spain or Portugal, that our reaction will be devastating and that the full force of NATO will be upon him".
"Nothing can replace America's nuclear umbrella, the guarantor of our security" - NATO Secretary-General Mark Rutte speaking at the Warsaw School of Economics this afternoon — @rtenews pic.twitter.com/DidaIrfvgH
— Liam Nolan (@liamnolanRTE) March 26, 2025
The NATO chief said that members of the military alliance that currently spend less than 2% of GDP on defence were having "genuine debates" to reach that target by the summer.
Mr Rutte said last month that NATO members will have to increase their defence spending to more than 3% of GDP, up from the current threshold of 2% set by the alliance more than a decade ago.
That spending target is likely to become a main discussion point at NATO's annual summit in The Hague in June.
US President Donald Trump has long criticised NATO members that failed to meet the 2% target and, before returning to the Oval Office in January, called for alliance members to ramp up defence expenditure to 5% of GDP.
Poland spends more on defence and security than any other European NATO member in terms of GDP, committing to 4.7% already this year.
Estonia and Latvia currently spend more than 3% of annual GDP on defence.
Earlier, Mr Rutte met Polish Prime Minister Donald Tusk and Polish President Andrzej Duda.
During a press conference with Mr Tusk, the NATO Secretary-General said that the alliance would respond with a "devastating" blow to any attack by Russia on Poland or another ally.
