President Donald Trump waits to enter Arlington National Cemetery's Memorial Amphitheater in Arlington, Va., May 29, 2017.

President Donald Trump waits to enter Arlington National Cemetery's Memorial Amphitheater in Arlington, Va., May 29, 2017. (Elizabeth Fraser/U.S. Army)

SEOUL, South Korea — President Donald Trump told China thanks for trying to help with North Korea but “it has not worked out,” in what analysts said may signal a possible policy shift days after the death of a U.S. student who had been detained by the isolated state.

Trump tweeted the message to Beijing on Tuesday, about two hours after saying he “condemns the brutality of the North Korean regime as we mourn its latest victim.”

The president has repeatedly called on China to intensify efforts to rein in its communist ally’s nuclear weapons program. The administration also has welcomed recent measures by his Chinese counterpart Xi Jinping, including the suspension of coal imports from the North.

But Pyongyang has remained defiant, test-firing more than a dozen missiles so far this year and raising fears it is making swift progress toward its goal of developing an intercontinental ballistic missile that could deliver a nuclear weapon to the U.S. mainland.

Analysts said the president may be sending a message that he is shifting toward a tougher approach despite his frequently stated preference to rely on China’s influence.

The tweet also came ahead of next week’s summit between Trump and new South Korean President Moon Jae-in.

“Trump declared the first phase of his North Korean policy is essentially over … although it begs the question ‘what’s phase two?’” said John Delury, an expert on China and the Koreas at Yonsei University in Seoul. “In this sense Trump’s tweet is positive because we really overemphasize China’s role in all of this.”

He also said it provided an opening for Moon, who has called for dialogue with the North and said he wants to play a leading role in the issue.

“South Korea has been completely out of the picture. I think it’s actually promising for Moon because we know that Moon wants to be more proactive,” Delury said.

Shin Du Chel, a political science professor at Hanyang University in Seoul, agreed.

“Trump seems to be sending a message to China that he’ll be switching to a stronger mode,” Shin said. “And Trump seems to have been sending a message to South Korea that it should cooperate with Washington ahead of the summit.”

Some U.S. officials, however, cautioned against reading too much into the tweet, which appeared ahead of a meeting between the U.S. and China to discuss North Korea, CNN reported.

China later insisted it has played a constructive role in dealing with North Korea. “In order to resolve the Korean peninsula nuclear issue, China has been making unremitting efforts and we have been playing an important and constructive role," foreign ministry spokesman Geng Shuang said in Beijing. "To sum up, our contributions are recognized by all and our efforts are indispensable." China has signed onto recent moves to tighten U.N. Security Council sanctions again Pyongyang. But it also fears pushing the regime too hard may spark instability in the region, including an influx of North Korean refugees and a united Korea that could bring U.S. troops to its doorstep.

The political messaging came as outrage mounted over the death on Monday of Otto Warmbier, a University of Virginia student who was in a coma when he was medically evacuated from North Korea to his family last week in Ohio following 17 months of detention for allegedly attempting to steal a propaganda poster.

Warmbier’s death comes at a sensitive time as the relatively new U.S. and South Korean administrations are still forging their policy toward North Korea, balancing the need for a tough stance against the weapons program with a desire for dialogue.

Moon expressed “deepest condolences” to Warmbier’s family and the American people in an interview with CBS News.

“We cannot know for sure that North Korea killed Mr. Warmbier. But I believe it is quite clear that they have a heavy responsibility in the process that led to Mr. Warmbier’s death,” he said.

Moon also said his policies were lining up with those of Trump when it comes to North Korea, saying he wants dialogue but first seeks a freeze of the communist state’s nuclear and missile programs.

”I believe that my position is not at odds with the policy of the United States or that of President Trump. It seems to me that President Trump has criticized the failed former policies of his predecessor administrations. And on that point, I have the same view as President Trump.”

Stars and Stripes reporter Yoo Kyong Chang contributed to this report. Twitter: @kimgamel

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