"One can say this friendship is irreplaceable," said Chinese President Xi Jinping of the relationship between China and North Korea.

China and North Korea have announced a deepening of diplomatic ties and strategic cooperation a day ahead of the Chinese leader's ‘historic visit’ to the upper peninsula, dampening United States attempts to peel away Chinese support toward the Korean nation.

On Wednesday, Chinese President Xi Jinping penned an op-ed for Rodong Sinmun, the newspaper of the ruling Korean Workers Party (WPK).

In the article, Xi pledged China’s support for North Korean Supreme Leader Kim Jong Un’s approach to peace efforts on the peninsula.

"We are pleased to see that with Chairman Kim's correct decisions and the concerted efforts of all parties concerned, the general trend of peaceful dialogue on the Korean Peninsula has taken shape, and a political settlement to the Peninsula issue sees a rare historical opportunity, which has been universally recognized and anticipated by the international community," stated President Xi as translated by Global Times.

Chinese state media, CGTN, also reports, “China will firmly support Kim's achievements in socialist construction by leading the WPK and the people through a new strategic route, focusing all his efforts on economic development and improving people's livelihoods.”

Xi's article was published the day before his first state visit to North Korea, and the first by any Chinese leader in 14 years.

On Tuesday, China and Russia jointly defended North Korea at a United Nations sanctions committee meeting and successfully blocked the U.S. from ​​​banning refined oil imports to North Korea. U.S. representaives accused the Korean nation of exceeding its limit of 500,000 barrels of refined oil agreed last year at by the U.N. members. However, China and Russia blocked the move, demanding the U.S. provide more robust evidence to its accusation.

The increasingly close ties between Xi and Kim may disappoint U.S. foreign policy analysts who had hoped China would pressure North Korea into backing down on a number of key issues.

Writing in 2013, Ted Galen Carpenter, a senior fellow for the neo-conservative Cato Institute, noted that China was growing "frustrated" with Kim’s government and U.S. foreign policy should be focused on exploiting the rift. “No one should be allowed to throw the region, even the whole world, into chaos for selfish gains,” Xi said several years ago regarding Kim's governing style.

Yet, as diplomatic and trade tensions grow between the U.S. and China, as well as with North Korea, the two Asian countries are now presenting a united front.

“One can say this friendship is irreplaceable,” President Xi described the North Korea-China relationship in his WPK-published letter.