South Korea's defense chief pledged Friday to strengthen the already strong alliance with the United States to ensure peace and stability on the Korean Peninsula amid growing threats from North Korea.

"The security situation on the Korean Peninsula is grave," Defense Minister Han Min-koo said in a meeting with defense experts, citing North Korean leader Kim Jong-un's New Year's message.

Kim said in his address that North Korea will firmly push forward nuclear and missile development programs. He set 2017 as the year of perfecting the communist nation's military capabilities. The leader said the country had reached the final stage of preparations to test fire an intercontinental ballistic missile, an apparent warning that it is perfecting the development of an ICBM capable of hitting the US homeland.

Han said maintaining a strong alliance with the US is the key to watertight security of South Korea.

His remarks came after retired Marine Corps Gen. James Mattis, incoming US President Donald Trump's pick for defense secretary, said Thursday the North's nuclear and missile development is "a serious threat and we've got to do something about it."

Mattis said the situation on the Korean Peninsula remains volatile amid the North's provocative statements and actions, including continued development of increasingly sophisticated ballistic missile capabilities and repeated threats to the US.

Incoming president Trump also reaffirmed the alliance with South Korea and filled some key posts in his government with people who value the alliance, such as Mattis and incoming National Security Advisor Mike Flynn.

Trump's statements on North Korean nuclear programs and Seoul-Washington alliance are meaningful because they are a "positive sign" for Seoul in seeking a partnership with the new administration over North Korea and strengthening the bilateral alliance, the minister said. (Yonhap)