Seoul, April 18 : Chinese President Xi Jinping has sent a letter to North Korean leader Kim Jong-un, expressing his willingness to strengthen strategic communication with the latter, Pyongyang's state media reported on Tuesday. Xi expressed his "heartfelt" thanks to the North's leader in a reply sent on April 12 to Kim's earlier message congratulating Xi's election as the Chinese president for a third term, according to the Korean Central News Agency (KCNA). Xi said China and the North have maintained and developed their traditional friendly relations, even though international and regional security situations are changing "seriously and in a complicated way", reports Yonhap news Agency The Chinese leader expressed his willingness to elevate the bilateral ties to a higher level by "strengthening the strategic communication and jointly guiding" the development of the Beijing-Pyongyang relations with the North's leader, the KCNA said. Kim sent a letter expressing his "warmest congratulations" to Xi on March 10, the day when he won an unprecedented third term as the Chinese president. Prior to last week's letter, Xi delivered a similar message thanking the North's leader earlier this month via China's new ambassador to North Korea, Wang Yajun. North Korea has been strengthening its ties with China, tits traditional ally and economic benefactor, amid global sanctions on its nuclear and missile programs, and stalled denuclearisation talks with the US. /IANS