South Korea has adopted a "firm approach" against Russia in the wake of the improving relations between Moscow and North Korea, according to the Institute for the Study of War.
The US thinktank believes that Russian efforts to threaten Seoul into withholding aid from Ukraine have failed.
South Korean national security director Chang Ho-jin said yesterday that the type of military support that South Korea will provide to Ukraine is contingent on the depth and evolution of Russian military cooperation with North Korea.
Mr Chang had previously said that the partnership between Russia and North Korea had encouraged South Korea to change its long-standing policy prohibiting the transfer of arms to Ukraine.
Vladimir Putin said last week that Seoul would be making "a very big mistake" if it decided to supply arms to Ukraine.
