China's Xi Jinping calls for 'deepening' ties with North Korea in letter to Kim Jong Un

SEOUL, Sept. 9 (UPI) -- Chinese President Xi Jinping vowed to strengthen communication and cooperation with Pyongyang in a letter to North Korean leader Kim Jong Un , state media reported Monday, despite signs of cooling relations between the neighbors in recent months.

Xi sent the letter, his first to Kim in over eight months, on the occasion of the 76th anniversary of the founding of North Korea.

"China and the DPRK are linked by the same mountain and rivers and the traditional friendship has been further consolidated with the passage of time," Xi wrote, according to state-run Korean Central News Agency.

The Democratic People's Republic of Korea is the official name of North Korea.

"The Chinese side will continue to view and deal with the China-DPRK relations at a strategic level and from a long-term angle," Xi wrote.

Xi added that Beijing will bolster "friendly and cooperative relations by deepening the strategic communication and boosting coordination and cooperation," KCNA reported.

The missive was the first from Xi since a New Year's greeting on Jan.1 and comes as the relationship between the longtime allies has appeared to fray in recent months.

China has long been North Korea's largest trade partner and international authorities say it continues to help Pyongyang skirt punishing economic sanctions. But Beijing has not thrown its weight behind the North's growing relationship with Russia, which centers around arms sales for Moscow's war in Ukraine.

In one sign of possible discord, North Korea responded angrily to a trilateral summit in May among China, South Korea and Japan, calling it a "grave political provocation" that would speed up a military confrontation.

Kim also received congratulatory messages for the anniversary from Russian President Vladimir Putin and a handful of other world leaders including Cuban President Miguel Diaz-Canel, KCNA said.

"I am sure that the comprehensive strategic partnership between Russia and the DPRK will be strengthened in a planned way thanks to our joint efforts," Putin wrote, according to KCNA.

"This undoubtedly conforms to the fundamental interests of the peoples of the two countries and will contribute to ensuring the security and stability in the Korean peninsula and the Northeast Asian region as a whole," he added.

Putin visited Pyongyang in June and the two leaders signed a defense pact that calls for extending military aid "without delay" if either country is attacked.

Cuba's Diaz-Canel sent a message in which he "reaffirmed the will to steadily strengthen the close ties of friendship, cooperation and solidarity between the two countries," KCNA said.

The correspondence comes after South Korea and Cuba established diplomatic relations in February for the first time since 1959 -- a move widely seen as a blow to the North, which had maintained a close bond with Havana since the Cuban Revolution. Pyongyang recalled its ambassador a month later for undisclosed reasons, but last month announced that it had appointed a new top envoy to Cuba.