President Trump appeared to interfere on Friday with sanctions the US put on two Chinese shipping companies as punishment for their illicit trade with North Korea.
Trump also tweeted Friday that he had "ordered the withdrawal of those additional sanctions".
The White House did not immediately respond to questions about which sanctions Trump was referring to.
Trump and North Korean dictator Kim Jong Un have met face to face twice, but left a summit in Vietnam last month without reaching a deal on denuclearization. Treasury Secretary Steven Mnuchin reaffirmed the Trump administration's commitment to "the final, fully verified denuclearization of North Korea" and warned that "shipping companies employing deceptive tactics to mask illicit trade with North Korea expose themselves to great risk". Each side has blamed the other, with the US saying North Korea demanded too much sanctions relief and Pyongyang faulting Washington for rejecting its promises to reduce its nuclear program.
In a tweet, he wrote that "the maritime industry must do more to stop North Korea's illicit shipping practices".
Kazianis said. "Trump's cancelling out of sanctions might have been a bid to get North Korea to change its thinking".
Washington announced the sanctions three weeks after a second meeting between President Donald Trump and North Korean leader Kim Jong-un broke down over conflicting demands by North Korea for relief from sanctions and from the USA side for Pyongyang to give up its nuclear weapons.
The sanctions were the first new sign of pressure since talks between Trump and Kim broke down in Hanoi.
One of the two Chinese shipping companies, Dalian Haibo International Freight Co.More news: Consumers should soon see benefit of Fed's patience on rates
Trump has sought to project to Kim that while some in his administration are skeptical, he is the ultimate decider and strikes a friendler posture, officials said.
Sen. Chris Van Hollen, D-Md., tweeted that Trump "is being played by Kim Jong Un".
The problem: The Treasury did not announce any new action affecting North Korea on Friday, let alone "additional large scale Sanctions".
Hours after the sanctions announcement, North Korea on Friday pulled out of a liaison office with the South, a major setback for Seoul.
North Korea has demonstrated its frustration with the outcome of the summit.
"Sidestepping his own Treasury Dept. and withdrawing sanctions against North Korea the same day they were announced defies logic", Van Hollen added.
South Korea's Unification Ministry said that the north was "pulling out with instruction from the superior authority".
The Treasury Department announced on Thursday it would be imposing new sanctions against Pyongyang, further restricting the isolated, nuclear-armed state's options for worldwide trade.
A United Nations panel on sanctions said in the report Liaoning Danxing had been suspected of illicitly shipping Mercedes-Benz limousines to North Korea.