"If we do use it on North Korea, it will be a very sad day for North Korea".
Pressure from Washington has ratcheted up since North Korea conducted its sixth and largest nuclear test on Sunday. "All opposing sides have enough common sense" to avoid it, he said, speaking alongside South Korean President Moon Jae-in and Japanese Prime Minister Shinzo Abe at the Eastern Economic Forum in the far eastern Russian city of Vladivostok on Thursday. Its sixth nuclear test on Sunday prompted the United States to speak about a "military response" and South Korea to conduct major military exercises.
Putin called on all North Korea's neighbours to show restraint, indicating the bellicose rhetoric and the military drills are only "playing into their hands".
Moreover, the shorter the space between each test, the less there is that North Korea's scientists and technicians can learn from them and make improvements to their designs, he said.
The North's official news agency again recently slammed pending sanctions by the United Nations, and Nikki Haley, the USA ambassador to the UN, for accusing North Korea's leader Kim Jong-un of "begging for war".
Critics also question THAAD's effectiveness, saying North Korea could try to overwhelm it with a massive barrage and its location will do nothing to protect Seoul. The latter conceded to the point that "war is no solution", adding, "Although the tension escalates in Korean Peninsula, I can assure everyone we are not headed for a war".
U.S. warns North Korea threats 'will be met with massive military response'
It was the sixth nuclear test conducted by the communist nation, but the first to occur since Trump took office. Earlier on Sunday, the president issued a series of tweets commenting on Pyongyang's sixth test.
Moon earlier called for a ban on overseas North Korean workers, who are a key foreign currency source for the North, but Putin said problem should be solved diplomatically, according to Seoul's presidential office.
South Korea's military said it was keeping close tabs on the North amid speculation it could stage a missile launch or another nuclear test to mark the 1948 establishment of the Democratic People's Republic of Korea.
Beijing says the system's powerful radars will be able to monitor flights and missile launches deep inside north-eastern China.
The South Korean government is expected to deploy several thousand police to accompany the missiles, in anticipation of resistance and possible confrontation. Seongju residents and activists have anxious over rumoured health hazards and the possibility of being targeted in North Korean attacks.
Jens Stoltenberg said Pyongyang must abandon its nuclear and missile programmes and refrain from further testing.
Federica Mogherini said a demilitarisation of the Korean peninsula should be achieved peacefully through dialogue and diplomacy.