Washington: US President Donald Trump said on Thursday he was "very disappointed that China is allowing oil to go into North Korea" and that such moves would prevent "a friendly solution" to the crisis over Pyongyang's nuclear program.

"Caught RED HANDED - very disappointed that China is allowing oil to go into North Korea. There will never be a friendly solution to the North Korea problem if this continues to happen!" Trump wrote in a post on Twitter.

China earlier on Thursday said there had been no UN sanction-breaking oil sales by Chinese ships to North Korea after a South Korean newspaper said Chinese and North Korean vessels had been illicitly linking up at sea to get oil to North Korea.

The Trump administration has led a drive to step up global sanctions on North Korea in response to Pyongyang's efforts to develop nuclear-tipped missiles capable of hitting the United States.