The United States on Tuesday sharply criticized China for not enforcing sanctions on North Korea and vowed to step up its own efforts, as hopes fade for a last-minute breakthrough under outgoing President Donald Trump.

The State Department launched a new website, DPRKrewards.com, that will offer payouts of up to $5 million for tips to boost sanctions on North Korea, including on businesses in China.

"I want to tell you more are forthcoming," Alex Wong, the US deputy special representative on North Korea, said of sanctions.

In a speech at the Center for Strategic and International Studies, Wong acknowledged that Pyongyang has not yet taken "any concrete steps toward denuclearization" and voiced alarm over its unveiling of a massive long-range missile at a parade in October.

North Korean leader Kim Jong Un presides over an October 10, 2020 military parade in which Pyongyang showcased a new long-range missile that has alarmed the United States
North Korean leader Kim Jong Un presides over an October 10, 2020 military parade in which Pyongyang showcased a new long-range missile that has alarmed the United States KCNA VIA KNS / -

"Lifting sanctions and pumping more revenue into the DPRK while its missile and nuclear production facilities continue to hum is something we will never do," said Wong, referring to the North by its official name, the Democratic People's Republic of Korea.

His hard-nosed assessment stands in contrast to the rosy statements by Trump, who has boasted that he prevented a catastrophic war and said he deserves the Nobel Peace Prize.

But Wong mostly took aim at China, a frequent target of the Trump administration, as he accused Beijing of ignoring UN sanctions that it itself voted for at the Security Council over its ally's missile and nuclear programs.

"The premature sanctions relief that Beijing can't achieve through the diplomatic front door, it is instead trying to achieve through the back door," Wong said.

North Korean state media shows an October 2020 rally to support an 80-day economic development campaign
North Korean state media shows an October 2020 rally to support an 80-day economic development campaign KCNA VIA KNS / STR

"The examples of this chronic failure are numerous, growing and worrying."

He said that US vessels provided information to Beijing 46 times since 2019 about North Korean fuel-smuggling in Chinese waters, and in the past year observed 555 cases of North Korean shipments of coal of other sanctioned exports to China.

"On none of these occasions did the Chinese authorities act to stop these illicit imports. Not once," Wong said.

Wong said that 20,000 North Korean workers still worked in China, going against UN-backed efforts to stop what is widely seen as slave labor that the regime exports for revenue.

US President Donald Trump meets North Korea's leader Kim Jong Un at the start of their historic June 2018 summit in Singapore
US President Donald Trump meets North Korea's leader Kim Jong Un at the start of their historic June 2018 summit in Singapore AFP / SAUL LOEB

China has been pushing to ease sanctions on North Korea, believing the regime should see incentives for denuclearization commitments, and is widely seen as fearing an economic implosion of its impoverished neighbor.

Trump has spoken in glowing terms about Kim, saying the two of them "fell in love" after their first summit in Singapore and could reach a historic deal.

But under pressure from aides, Trump refused to loosen sanctions at a second February 2019 summit in Hanoi.

Kim later warned that he would no longer be bound by a self-imposed moratorium on nuclear and long-range missile tests, although he has not followed through on his threats.

Wong's remarks preview what will likely be a more low-key diplomatic approach on North Korea by President-elect Joe Biden, who has accused Trump of validating a "thug" by meeting Kim.

North Korea, which has a history of flexing its muscle as new US presidents take over, is one of the last countries not to congratulate Biden. State media have hardly set a welcoming tone, earlier calling Biden a "rabid dog" who "must be beaten to death."

Aid groups have voiced growing fears about the humanitarian situation in North Korea, where at least hundreds of thousands of people died in a famine in the 1990s.

Katharina Zellweger, the former North Korea country director for the Swiss Agency for Development and Cooperation, told the think-tank event that the Covid-19 lockdown had worsened distribution of necessities in a country where 40 percent of people remain food insecure.

She voiced concern about the sanctions, saying they had knock-on effects even though humanitarian goods are exempt.

"The whole economy suffers because of import and export restrictions and ordinary people are feeling the pain," said Zellweger, who now runs non-governmental group KorAid.