President Trump said Wednesday that China took a “big step” in easing tensions between the two nations by turning away North Korean coal ships the day before and returning them to their home port of Nampo.

At a joint press conference with NATO Secretary General Jens Stoltenberg on Wednesday, Trump described his relationship with Chinese President Xi Jinping as one with “good chemistry” and praised China’s apparent commitment to banning coal imports from North Korea.

“We have a very big problem in North Korea and as I said, I really think that China is going to try very hard, and has already started—a lot of the coal boats have already been turned back—you saw that yesterday and today—they’ve been turned back,” Trump said.

“The vast amount of coal coming out of North Korea going to China, they’ve turned back the boats—that’s a big step and there are many other steps I know about so we’ll see what happens, it may be effective, it may not be effective—if it’s not effective, we will be effective—I can promise you that.”

Reuters first reported the North Korean ship movement Tuesday. According to Reuters, China banned all imports of North Korean coal on February 26—cutting off the country’s most important export product—after repeated missile tests from the isolated nation that drew criticism from around the globe.

A senior defense official told Fox News on Wednesday that the Reuters report was “credible.”

While the White House said it would not comment on the Reuters report, State Department spokesman Mark Toner told Fox News that all UN Member States are required to implement sanctions resolutions in good faith, and that the U.S. “expects them to do so.”

“Full implementation of this resolution will demonstrate global consensus in imposing stronger sanctions on North Korea’s sources of revenue for its UN-proscribed nuclear, ballistic missile, and proliferation programs,” Toner said in an email to Fox News.

The report also suggested that China’s ban of North Korean coal could be beneficial to the U.S. economy, if the U.S. makes up the difference and considers selling coal to China.

According to Reuters data, there was no U.S. coking coal exported to China between late 2014 and 2016, but shipments rose to over 400,000 tons by late February, amid Trump’s repeated commitment to restoring the U.S. coal industry and rolling back Obama-era coal regulations.

Under the Obama administration, the coal mining industry lost approximately 36,400 jobs, and between 2009 and 2015, the number of coal mines in the U.S. declined by 554, leaving 853 mines in the U.S. by 2015, down from the 1,407 in 2009.

Last month, the president signed an executive order to “end the war on coal” and lift the ban on federal leasing for coal production, as well as the “job-killing restrictions” on the production of clean coal and other energy sources.

“We’re going to have clean coal—really clean coal,” Trump said at the signing of the Executive Order to Create Energy Independence.”

Fox News' Lucas Tomlinson contributed to this report.