Trump says China tried but failed to pressurize North Korea
What's the story
US President Donald Trump said China's efforts to pressurize North Korea into slowing down its nuclear weapons program have failed.
However, Trump tweeted that he "greatly appreciated the efforts of President Xi & China to help with North Korea, it has not worked out. At least I know China tried!"
Trump had high hopes for increased cooperation against North Korea.
Background
US strategy on North Korea relied on China's participation
In April, Trump welcomed his Chinese counterpart Xi Jinping for bilateral talks in Florida.
Trump had sought Xi's assistance in persuading North Korea to halt its ballistic missile and nuclear weapons programs.
After their meeting, Trump had praised Xi over his handling of the North Korea.
Secretary of State Rex Tillerson had also said Washington's North Korea strategy relies on Chinese action.
Details
Trump's tweet signals his frustration on North Korea
It remains unclear what Trump meant by his tweet on China and S.Korea.
Former US ambassador to South Korea Christopher Hill said, "I think the president is signaling some frustration."
"He's signaling to others that he understands this isn't working, and he's trying to defend himself, or justify himself, by saying that at least they tried as opposed to others who didn't even try."
Weapon test?
North Korea may be preparing to conduct another nuclear test
Trump's tweet comes a day after an unnamed US official said movements were detected recently near a tunnel entrance of a North Korean nuclear test site by US spy satellites.
It remains unclear whether these movements were preparations for another nuclear test.
"North Korea remains prepared to conduct a sixth nuclear test at any time," a South Korean Defense Ministry official had said.
Explained
More pressure on China to act on North Korea
Trump's tweet will likely increase pressure on Beijing ahead of high level bilateral meeting between diplomatic and military officials from both America and China in Washington on Wednesday.
The US is expected to urge Beijing to impose stricter sanctions on North Korea, including an oil embargo and ban on its guest workers in China.
China has previously resisted such moves.
Otto Warmbier
Released US student death casts a shadow
Trump has hardened his rhetoric following 22-year-old US college student Otto Warmbier, who had died after spending 17 months as a prisoner in North Korea.
Trump had said North Korea is a "brutal regime and we'll be able to handle it."
Meanwhile, the White House said chances of a meeting between Trump and North Korean leader Kim Jong-un are less likely following Warmbier's death.