155 millimeter artillery shells are placed in a pile at a position of Ukrainian servicemen near a front line, amid Russia's attack on Ukraine, in Zaporizhzhia region, Ukraine, Jan. 14. Reuters-Yonhap

U.S. think tank experts floated the idea Monday of the United States tapping into South Korea's 105 millimeter munitions stockpile to support Ukraine's fight against Russia, as Kyiv urgently needs artillery ammunition supplies in the ongoing war of attrition.

Mark Cancian, a senior adviser at the Center for Strategic and International Studies (CSIS), and Chris Park, a CSIS research assistant, made the suggestion, noting that South Korea likely cannot spare more 155 mm shells due to North Korean threats, and that its military is transitioning most artillery units to 155 mm platforms.

"A U.S. proposal to use the bulk of South Korea's 105 mm munitions stockpile, followed by replacing them with the currently in-production 155 mm ammunition, could appeal to South Korea," they wrote in a commentary posted on the CSIS website.

They pointed out that last year, Washington worked with Seoul to send over 300,000 155 mm shells to Ukraine.

South Korea is known to have provided the U.S. with the munitions on condition that the U.S. is their "end user" -- a method that observers said might have enabled Seoul to give indirect arms support to Ukraine while maintaining its principle of non-lethal aid to Ukraine at least on the surface.

"The administration may need to re-tap the South Korean munitions stockpile to arm Ukraine in the face of dwindling stockpiles and congressional inertia," the experts said.

The experts said that as Western 155 mm artillery stockpiles dwindle, the U.S. and others have provided Ukraine with 105 mm howitzers and ammunition.

Citing public reports, they noted that South Korea may have around 3.4 million 105 mm artillery shells.

"These munitions would be compatible with all the 105 mm howitzers Ukraine operates," they said.

They also said that lending 105 mm shells are unlikely to hurt the South Korean military's readiness.

"Less than 30 percent of howitzers operated by the South Korean military shoot 105 mm ammunition and the South Korean military is transitioning most units to 155 mm self-propelled howitzers like the domestically produced K9 Thunder," they said.

The U.S. government has expressed appreciation for South Korea's continued support for Ukraine, but said that whether to send munitions to Ukraine is a sovereign decision for Seoul to speak to. (Yonhap)