Amid increased concerns over nuclear warfare, North Korea issued a threat Monday against the West, vowing to “pour further misery” on the United States. The intimidation came on the 29th anniversary of North Korea capturing an American intelligence ship, the USS Pueblo, during the Cold War.

“The U.S. will face a position more miserable than that in the Pueblo case if it forgets that lesson and frantically pursues new ways to provoke war against the north,” said North Korea’s Central TV station.

The threat followed President Donald Trump’s Friday announcement that the U.S. would be developing a “state of the art” missile defense system to protect against attacks from North Korea. The administration revealed the plans on its website, though no exact details were released.

In the meantime, South Korea emphasized the need for defense against its northern neighbor.

“Its nuclear and missile capabilities are developing at an unprecedented rate,” said South Korea’s acting president, Hwang Kyo-Ahn. “They are a real and obvious threat. They are also miniaturizing nuclear weapons.”

GettyImages-509467228 South Korean protesters burn pictures of Kim Jong Un during an anti-North Korea rally in Seoul, South Korea, Feb. 11, 2016. Photo: Getty

South Korea called Monday for the immediate deployment of its anti-missile defense system, known as Terminal High Altitude Area Defense (THAAD). The system was agreed upon by the U.S. last year, but hesitation from China led South Korean officials to put it on the backburner. China was concerned that THAAD’s far-reaching radar could infringe on its own territory.

North Korean leader Kim Jong Un has made no secret of his country's nuclear proliferation. Despite sanctions by the United Nations, Pyongyang fired an average of two ballistic missiles every month in 2016 and conducted at least two nuclear tests. A report issued earlier in January by the South Korean Ministry of National Defense alleged that North Korea increased its supply of plutonium by such large amounts over the past two years that the country now has enough power for 10 nuclear warheads.