By Olena Harmash and Tom Balmforth

KYIV (Reuters) - Russia has begun using North Korean troops in significant numbers for the first time to conduct assaults on Ukrainian forces battling to hold an enclave in Russia's Kursk region, President Volodymyr Zelenskiy said on Saturday.

The Ukrainian leader said the more active use of the troops was a new escalation in the war and called for a global response, as Donald Trump's return to the White House next month fuels speculation of a coming push for peace talks.

"Today, we already have preliminary data that the Russians have begun to use North Korean soldiers in their assaults. A significant number of them," Zelenskiy told Ukrainians in his daily wartime address.

The North Koreans were being used in combined Russian units and only on the Kursk front for now, he said, adding: "We have information suggesting their use could extend to other parts of the front line."

Kyiv first said North Korean forces turned up in Russia's Kursk region in October and later reported unspecified clashes and casualties. It estimates there are 11,000 North Koreans in total, adding to a force of tens of thousands of Russians.

Russia has neither confirmed nor denied the presence of North Koreans on its side.

Ukraine, nearly a fifth of which is occupied by Moscow's troops, launched an incursion into Russia's western Kursk region in August, carving out an enclave that it said could be used as a bargaining chip in any talks to end the war.

Ukraine has battled to hold the area, although some Western military analysts have questioned the incursion's rationale, arguing it has extended an already-sprawling front line, exposing Ukraine's manpower weakness as it battles a larger foe.

Kyiv said the operation sought to divert Russian forces, but it has not stopped Moscow notching up its fastest gains in the east since 2022, although Russian forces have taken heavy casualties, according to Kyiv and the West.

POTENTIAL ENDGAME

Ukraine's General Staff reported a significant increase in the number of Russian assaults on the Kursk front, along with airstrikes, glide bomb raids and more than 200 artillery attacks.

Andrii Kovalenko, an official at Ukraine's National Security and Defence Council, said the North Koreans had taken losses, but provided no numbers.

"The Russians are counting on numbers and are trying to carry out assault operations with the help of the Koreans, when the task of the Koreans is to run under the blows of our forces and occupy certain areas," Kovalenko wrote on Telegram.

As Trump's return has put the focus on a potential endgame in the war, Kyiv has urged the West to put it into a stronger position and bridled at fears of escalation, a line echoed by Zelenskiy as he denounced North Korea's role in the fighting.

"In essence, Moscow has dragged another state into this war, and to the fullest extent possible. And if this is not escalation, then what is the escalation that so many have been talking about?" Zelenskiy said.

He used his address to issue a fresh appeal to his allies to strengthen their support for Kyiv, something he said he would discuss with European powers next week.

Zelenskiy plans to attend a meeting with the leaders of Britain, France, Germany, Italy, Poland, NATO, and the EU in Brussels on Wednesday.

(Reporting by Olena Harmash; Writing by Tom Balmforth; Editing by Gareth Jones, Conor Humphries and Giles Elgood)