Chinese President Xi Jinping vowed efforts to further develop his country's relationship with North Korea and support the North's struggle to advance its socialist agenda, the North's state media reported Saturday.

Xi's remarks came in a letter to North Korean leader Kim Jong-un, marking the 75th founding anniversary of the North's ruling Workers' Party of Korea (WPK).

"I extend warm congratulations and the best wishes to Comrade Chairman (Kim) and through you to the Central Committee of the WPK and all members of the WPK and the Korean people on behalf of the Central Committee of the Communist Party of China and on my own behalf on the occasion of the 75th founding anniversary of the WPK," the Chinese leader wrote, according to the North's Korean Central News Agency (KCNA).

"In recent years under the reliable leadership of the Central Committee of the WPK headed by Comrade Chairman, the Party and people of Korea have put efforts on strengthening the Party building and the economic work, have coped with all sorts of hardships and challenges in single-minded unity and conducted active exchange and cooperation with foreign countries to make a series of important achievements, while making steady advance along the path of socialism," Xi added.

China is North Korea's largest communist neighbor and trade partner, accounting for more than 80 percent of the impoverished North overall imports and exports.

Beijing is also often criticized for failing to faithfully implement U.N. Security Council sanctions on North Korea.

Xi's letter to Kim comes amid wide speculation that the communist North may unveil a new advanced weapons system at its military parade, expected to take place later in the day.

Xi noted China-North Korea relations have reached a "new historic page" following his meetings with Kim in recent years.

"We have an intent to successfully defend, consolidate and develop China-Korea relations together with Korean comrades and propel the long-lasting and stable development of the socialist cause of the two countries and thus provide the two countries and the two peoples with greater happiness and make new and active contributions to realizing regional peace, stability, development and prosperity," he wrote, according to the KCNA.

"I wish Comrade Chairman good health and success in your work. I hope that the WPK would make ceaseless development and the socialist cause of Korea would prosper." (Yonhap)