Ukrainian President Volodymyr Zelenskyy said Thursday his government has intelligence information that 10,000 troops from North Korea are being prepared to join Russian forces fighting against his country, warning that a third nation wading into the hostilities would turn the conflict into a “world war.”

Zelenskyy did not go into detail about the claim that came a day after U.S. Deputy Secretary of State Kurt Campbell said that Washington and its allies are alarmed by North Korea's military support for Russia’s war in Ukraine but couldn’t confirm Ukrainian claims that soldiers were sent to fight for Moscow.

“From our intelligence we’ve got information that North Korea sent tactical personnel and officers to Ukraine,” Zelenskyy told reporters at NATO headquarters. “They are preparing on their land 10,000 soldiers, but they didn’t move them already to Ukraine or to Russia.”

Earlier, he warned that any North Korean involvement would be "the first step to a world war.”

NATO Secretary-General Mark Rutte said the allies "have no evidence that North Korean soldiers are involved in the fight. But we do know that North Korea is supporting Russia in many ways, weapons supplies, technological supplies, innovation, to support them in the war effort. And that is highly worrying.”

The Ukrainian leader’s comments raised the stakes for his Western allies as he met in Brussels with European Union leaders and then NATO defense ministers to discuss his “ victory plan ” to end the country’s devastating war with Russia.

Major points of the plan include an invitation for Ukraine to join NATO and permission to use Western-supplied longer-range missiles to strike military targets deep inside Russia, steps that have been met with reluctance by Kyiv’s allies so far.

“Ukraine truly deserves to become the 33rd NATO member one day, and we must do everything to ensure this happens," Zelenskyy said in an appeal at the alliance's headquarters. "Ukrainians have shown that we can defend shared values, and we are standing against Russia, the biggest threat to Europe and global peace.”

He told EU leaders that “we can end this war no later than next year” if his plan is followed. Zelenskyy told reporters that the plan aims “to strengthen Ukraine" and pave the way for a diplomatic solution to end the conflict on Europe's eastern flank.

“This plan doesn’t depend on Russian will, only on the will of our partners,” he said.

In a statement after their talks with Zelenskyy, the EU leaders called for a “rapid stepping up of military support and acceleration in its delivery, in particular air defense systems, ammunition and missiles” to protect Ukraine’s population and energy infrastructure.

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“Russia must not prevail,” the statement said.

The EU is a key supporter of Ukraine, a candidate member of the 27-nation bloc, as it fights Russia's invasion that began more than 2 1/2 years ago.

Zelenskyy had outlined the five-point plan to Ukraine’s parliament on Wednesday without disclosing confidential elements that have been presented in private to key allies, including the United States.

Hungarian Prime Minister Viktor Orbán, widely seen as having the warmest relations of any EU leader with Russian President Vladimir Putin, called Zelenskyy's plan “more than frightening” in a Facebook post. He said he would urge major EU powers France and Germany to “begin negotiations with the Russians as soon as possible, in order to find a way out of this situation.”

Rutte said Kyiv can rest “absolutely assured that 32 allies are united in making sure that collectively, we will do whatever is needed to make sure that Ukraine can prevail, that Putin will not get his way.” He reiterated that Ukraine’s place is among NATO’s ranks, but would not say when it might join.

Zelenskyy told EU leaders that his troops must keep battling Russian forces in Ukraine "while also bringing the war back into Russia so that Russians can feel what war is like and begin to hate Putin for it.”

Zelenskyy said he needs to "move some partners forward” on the issue. “And I think only with the unity in EU we can move and can move not only EU leaders, we can move other leaders.”

Thursday's talks in Brussels come as Ukrainian troops are struggling to hold off better-equipped Russian forces, especially in the eastern Donetsk region where they are gradually being pushed back. Kyiv is surviving with Western help, but Ukraine says it is coming too slowly.

Lithuanian President Gitanas Nauseda criticized slow Western decision-making over Ukraine and said it “would be a great mistake to think that our hesitance is the best way to de-escalation.”

At their summit in Washington in July, the 32 NATO members declared Ukraine on an “irreversible” path to membership.

But for now, NATO is in a holding pattern. Its biggest and most powerful member, the United States, is facing a presidential election. European allies expect little movement on Ukraine until a new president takes office in January.

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Beyond that, the United States and European heavyweight Germany remain deeply concerned about being dragged into a wider war with nuclear-armed Russia, and they lead a group of countries that oppose allowing Ukraine to join NATO until the conflict ends.