Linda Thomas-Greenfield, the United States Ambassador to the United Nations, on Tuesday delivered a concise yet stern message to China and Russia not to hide and reward North Korea's bad behavior. She also urged Pyongyang to "say yes" to Washington's repeated calls for dialogue without preconditions.

"Hiding the truth does not change it. Rewarding bad behavior only encourages it," Thomas-Greenfield conveyed pointed admonition to China and Russia during her visit to the heavily fortified Demilitarized Zone that separates the two Koreas, which are still technically at war.

"We urge Russia and China to reverse course and once again to urge Pyongyang to choose diplomacy and come to the negotiating table..."

Thomas-Greenfield in particular denounced China and Russia for capitalizing on their position as veto-wielding permanent members of the UN Security Council to "shield the DPRK from accountability," referring to North Korea by its official name, the Democratic People's Republic of Korea.

The ambassador underscored that the most recent instance entails the two countries preventing "all UN member states from learning about the DPRK's unlawful weapons program and sanctions evasion efforts."

Thomas-Greenfield's four-day trip to South Korea from Sunday came after Russia's recent exercise of its veto on March 28 to block the yearly extension of a panel of experts responsible for monitoring the enforcement of UN Security Council resolutions on North Korea. The 1718 Committee Panel of Experts also releases reports on cases that bypass UN sanctions twice a year.

China opted to abstain from the vote.

Exploring alternatives to the panel of experts, whose mandate will be terminated on April 30, was therefore a key topic for a series of meetings with President Yoon Suk Yeol and South Korean officials, including Foreign Minister Cho Tae-yul and Defense Minister Shin Won-sik, on Monday.

Thomas-Greenfield said the US is working closely with South Korea, Japan and other like-minded council members to "look at some creative ways, some out-of-the-box thinking," on how they might move forward in continuing the important work that the panel of experts was able to do.

"We're looking at any number of options," she told reporters.

"So whether that's the General Assembly or entities outside of the UN, I think we have to consider all possibilities."

The ambassador highlighted a potential option, which involves excluding China and Russia from participating in the new monitoring mechanism.

"If they can't veto it, then they will see it as a Western-led effort," she said, referring to China and Russia.

"But if we have to, we'll lead that effort to find a path to getting to the truth of what is happening in the DPRK as it relates to violations of sanctions."

Thomas-Greenfield delivered the message to North Korea after observing North Korean armed soldiers standing guard face-to-face with a security battalion composed of South Korean and US guard forces in the Joint Security Area — the sole location where soldiers from both Koreas stand in direct confrontation.

"This is the most heavily armed border in the world, and yet within it, there exists this strip of land for the purpose of maintaining peace so that even while military forces stare each other down, they have a place to come to the table and talk," Thomas-Greenfield said.

"It exemplifies what has become a kind of mantra for me this past year: 'Diplomacy is hard,' but there's a second half to that sentence: 'Diplomacy is hard, but it's worth it.'"

The US envoy also visited the blue conference building of the United Nations Command Military Armistice Commission straddling the inter-Korean border in the Joint Security Area in the DMZ.

Thomas-Greenfield mentioned observing negotiating tables and chairs empty at the blue building, stating that the US has reiterated to the North Koreans over and over again that we are ready to return to the negotiating table.

"Let me repeat: dialogue without preconditions," she said.

"All the DPRK has to do is say yes and show up to the table in good faith because our goal ultimately is to achieve a peaceful and stable peninsula and a peaceful and stable world."

By Ji Da-gyum and Joint Press Corps