Ever since their first real-life encounter earlier this month, US president Donald Trump has been touting the “great chemistry” he has with his Chinese counterpart, Xi Jinping.

Xi might feel less enthusiastic. In their latest call, which took place during Beijing’s morning today (April 24), Xi urged Trump to show restraint over the issue of North Korea, which might be preparing its sixth nuclear test for a military holiday being held tomorrow. The two leaders also discussed China’s troublesome neighbor at their Mar-a-Lago meeting and during a follow-up call.

On April 12 Trump told the Wall Street Journal (paywall) that he has offered Xi better trade deals in exchange for help on confronting North Korea. “We have a great chemistry together. We like each other. I like him a lot. I think his wife is terrific,” he said.

Last week Trump sat down with the Associated Press to talk about the first 100 day of his administration. This time he also used the phrase “great chemistry” to describe his relationship with other world leaders, including Egyptian president Abdel-Fattah el-Sisi and German chancellor Angela Merkel (whom Trump awkwardly ignored while she tried to shake his hand at the White House last month).

Of course Xi was on the list, too. When asked to elaborate on his “chemistry” with Xi, Trump took China’s hardening stance against North Korea as an example:

“Look, he [Xi] turned down many coal ships. These massive coal ships are coming where they get a lot of their income. They’re coming into China and they’re being turned away. That’s never happened before. The fuel, the oil, so many different things.”

There appears to be some truth about the coal. As for the oil, that’s less clear.

In February, China announced a ban on coal imports from North Korea, following the rogue nation’s then-latest missile test and alleged assassination of its ruler’s half-brother. After the Trump-Xi meeting, Chinese customs authorities reportedly ordered domestic firms to return North Korean coal shipments, although it appears such shipments were also being turned back before then. Official data also show Chinese imports of North Korean coal halved in the first quarter from a year ago. Beijing said in late February that by doing this it was complying with UN sanctions adopted in November, which it had not been strictly following.

Things are different when it comes to oil. North Korea relies almost entirely on China for its oil supply, and would suffer greatly without it. Beijing appears to have neither frozen nor reduced oil exports to its isolated neighbor. Doing so remains an option to punish Pyongyang for another nuclear test, according to Chinese experts and state newspapers, but their stances don’t necessarily reflect official policy.

Meanwhile Trump said he has backtracked from his threat to label China a “currency manipulator” not only because Xi is working with him on containing North Korea, but also because China has stopped artificially lowering its currency since Trump took office. He told AP:

“But President Xi, from the time I took office, he has not, they have not been currency manipulators. Because there’s a certain respect because he knew I would do something or whatever.”

He went on to say that, since he became president, Beijing has used a “very specific formula” to prop up its currency. But it’s unclear what he’s referring to. China stopped keeping its currency artificially low about 10 years ago. Since 2015, China’s central bank has started to strengthen the yuan’s value in an attempt to combat capital outflows amid the nation’s economic slowdown, and indeed has spent about $1 trillion in that effort.