SEOUL, South Korea (AP) — South Korea's president said Thursday his government “will not stand idle” as North Korea reportedly sends troops to support Russia War against Ukraineas he met with the Polish leader to discuss expanding defense cooperation amid the ongoing conflict.

The meeting between South Korean President Yoon Suk Yeol and Polish President Andrzej Duda came a day after U.S. and South Korean officials said they believed it would happen 3,000 North Korean soldiers were sent to Russia and train at several locations.

South Korea's spy service told lawmakers that North Korea expects to send a total of 10,000 soldiers to Russia by the end of the year.

Both Moscow and Pyongyang denied the presence of North Korean troops.

“We agreed that North Korea's deployment of troops in Russia, which is a direct violation of the UN Charter and UN Security Council resolutions, constitutes a provocation that threatens global security,” Yoon said after the summit.

Yoon said South Korea will work with allies and partners to prepare countermeasures that could be implemented gradually depending on the level of military cooperation between Pyongyang and Moscow.

Yoon's office said earlier this week that South Korea was considering various diplomatic, economic and military options, including supplying defense and offensive weapons systems to Ukraine.

South Korea, a growing arms exporter, has provided humanitarian aid, among other things non-lethal support for Ukraine and supported US-led economic sanctions against Moscow. But Seoul has not directly supplied Ukraine with weapons, citing a longstanding policy of not supplying weapons to countries actively involved in conflict.

Tensions on the Korean Peninsula have worsened since 2022 after North Korean leader Kim Jong Un used Russia's invasion of Ukraine as a distraction to accelerate the growth of his nuclear weapons and missile programs.

Seoul is also worried, with experts saying the North could seek major technology transfers in return for sending troops, including Russian know-how on intercontinental ballistic missiles and submarines, which would increase the threat of Kim's nuclear arsenal.

During their summit, Yoon and Duda agreed to “actively support” additional deliveries of South Korean military equipment to Poland, including a new contract for Korean K-2 tanks that the governments plan to finalize later this year, Yoon's office said.

Poland has signed a number of Gun shops Over the past two years, South Korea has worked with South Korea to acquire tanks, howitzers and rocket launchers to bolster its military capabilities following Russia's invasion of Ukraine.