South Korea's Chosun Ilbo newspaper this week quoted South Korean government sources as saying that spy satellites had detected 30 instances of ship-to-ship transfers to North Korean vessels since October.
A senior administration official told CNN that the Trump administration is planning to be "more quiet" and "more discreet" about speaking publicly on United States military exercises with the Republic of Korea and Japan aimed at demonstrating military capability against North Korea.
Trump's key to North Korea, however, has always been China and his personal relationship with Xi. Fox News summarized the Korean paper's report on Wednesday.
"Caught RED HANDED - very disappointed that China is allowing oil to go into North Korea", Trump tweeted.
Members of the Trump administration have repeatedly vowed to stop North Korea's nuclear program - and have not ruled out a military option that some analysts fear could lead to a nuclear conflict.
The UN Security Council last week unanimously imposed new sanctions on North Korea for a recent intercontinental ballistic missile test, seeking to further limit its access to refined petroleum products and crude oil. There will never be a friendly solution to the North Korea problem if this continues to happen!
President Donald Trump warned that illicit Chinese oil sales to North Korea may jeopardize a "friendly solution" to the confrontation over North Korean leader Kim Jong-Un's nuclear weapons and missile programs.
The US-drafted resolution bans the supply of almost 75 percent of refined oil products to North Korea, puts a cap on crude deliveries and orders North Korean nationals working overseas to be sent back by the end of 2019. Just two weeks ago, Trump credited China for its help in the US -led pressure campaign against Pyongyang, including support for three U.N. Security Council resolutions this year - the latest last week - over the North's nuclear and missile tests.
The Treasury statement came alongside the announcement of a series of sanctions against a range of North Korean entities and individuals.
According to South Korean government sources, the satellites have pictured large Chinese and North Korean ships illegally trading in oil in a part of the West Sea closer to China than South Korea.