Anchor: Russian President Vladimir Putin has warned South Korea that it would be making a "big mistake" if it supplies lethal weapons to Ukraine. Putin made the remark during a trip to Vietnam after South Korea condemned a new defense pact signed by North Korea and Russia and said it would review the possibility of supplying arms to Ukraine.
Kim Bum-soo has more. 

Report: National Security Adviser Chang Ho-jin said Seoul will reconsider the issue of providing arms support to Ukraine.  

Wrapping up his trip to Vietnam on Thursday, Russian President Vladimir Putin quickly responded, saying such a move would be a "big mistake."

[Sound bite: Russian President Vladimir Putin (Russian-English)]
"With regard to deliveries of lethal weapons to Ukraine for combat zones, this would be a very big mistake. I hope this does not happen... "
"If that happens, then we will take the according decision, which the current leadership of South Korea will probably not like."

The exchange comes in the wake of Putin's recent trip to North Korea, during which Pyongyang and Moscow signed a new pact to come to each other’s defense in the event of war. 

[Sound bite: Russian President Vladimir Putin (Russian-English)]
"Those who send these [missiles to Ukraine], think that they are not fighting us, but I said, as I did in Pyongyang, that we in that case reserve the right to supply weapons to other regions of the world, with regard to our agreements with the DPRK. I do not rule out sending weapons to North Korea." 

At the United Nations in New York, South Korean Foreign Minister Cho Tae-yul denounced the North Korea-Russia agreement.

[Sound bite: S. Korean Foreign Minister Cho Tae-yul]
(Reporter: Have they crossed a red line?)  
"... any direct or indirect, assistance or cooperation that enhances North Korea's military capability is a clear violation of the multiple UN Security Council resolutions. And it is indeed deplorable that a permanent member of the Security Council, which had agreed to the adoption of these resolutions, is now acting in violation of the resolutions... "

The foreign ministry in Seoul on Friday summoned the Russian ambassador and lodged a formal protest.

A presidential official in Seoul told reporters that there is a range of options in supplying weapons to Ukraine, and the government's future course of action depends on how Moscow approaches the situation. 

Analysts say Putin and North Korean leader Kim Jong-un during their meeting boosted their ties to the strongest level since the end of the Cold War. 

Seoul and Washington say North Korea is already supplying ammunition, rockets and other military supplies to help Russia in its war against Ukraine, possibly in exchange for receiving Russian military technology. North Korea and Russia deny the arms trade, which is a violation of UN sanctions. 
Kim Bum-soo, KBS World Radio News.