Chinese President Xi Jinping / Reuters

China's failure, if not refusal, to implement U.N. sanctions aimed at denuclearizing North Korea may be delaying the process, a senior U.S. diplomat said Tuesday.

Alex Wong, deputy assistant secretary of state for North Korea, insisted China often "chooses" not to implement the sanctions imposed by the U.N. Security Council, of which it is a permanent member.

"It (China) has the resources to implement its UN sanctions obligations. But again, it chooses not to," Wong told an online seminar hosted by the Center for Strategic and International Studies, a Washington-based think tank.

Just over the past year, Wong noted, there were 555 occasions where ships suspected of carrying coal or other sanctionable goods from North Korea reached China with the Chinese authorities doing nothing to stop them.

"One thing I can say is that Beijing's failures to meet its obligations is in direct contravention of China's professed desire to support a denuclearized and peaceful Korean Peninsula. If it truly wants the latter, it must do former," he told the webinar.

To help expose sanctions evasion activities by North Korea, the U.S. State Department has since June 2019 offered up to a US$5 million reward for information on such activities.

The State Department on Tuesday launched a website specifically dedicated to such information, according to Wong.

"Today, the State Department is launching a new website, DPRKrewards.com, through which individuals across the globe (can) provide information to our rewards for justice program on DPRK sanctions evasion," he said.