An international coalition of American allies will start “detecting and disrupting” North Korean oil smuggling operations at sea, a top U.S. diplomat announced Saturday.

“The United States has deployed aircraft and surface vessels to detect and disrupt these activities,” State Department spokeswoman Heather Nauert said in a news release.

That comes on the heels of a pledge by three U.S. allies to enhance the surveillance of North Korean oil tankers. Japan, Australia, and New Zealand, announced Friday they would aid “monitoring and surveillance activities against illicit maritime activities,” with a particular focus on ship-to-ship transfers of oil.

That sets the stage for a confrontation with Russia and China, who persist in selling oil to North Korea despite western assessments that they’ve breached an annual cap imposed by the United Nations Security Council.

“North Korea continues to regularly employ deceptive tactics to evade UN sanctions,” Nauert said. “Accordingly, UN Member States are required to prohibit persons or entities subject to their jurisdiction from engaging in ship-to-ship transfers of refined petroleum. In addition, the United States will not hesitate to impose sanctions on any individual, entity, or vessel supporting North Korea’s illicit activities, regardless of nationality.”

The sale of oil to North Korea has sparked intense controversy at the United Nations. China and Russia have rebuffed U.S. analysis that North Korea has breached the U.N. cap, an offense that would trigger an immediate oil embargo under the sanctions. Japan published photographs in May of an apparent Chinese-flagged vessel transferring oil to a blacklisted North Korean tanker. More recently, Ambassador Nikki Haley accused Russia, in particular, of “systematic” violations of the North Korea sanctions.

“Now is the wrong time to undo all the good work we’ve done in the Security Council,” Haley said Monday. “Now is the wrong time to ease sanctions pressure on the North Korean regime by repealing sanctions. And it’s never the right time to allow cheating to go unpunished.”

Nauert’s announcement raises the prospect of the U.S. or allies interfering with Russian or Chinese-flagged ships that transfer oil to North Korean tankers, as President Trump’s team tried to advance negotiations to dismantle the regime’s nuclear weapons and ballistic missile programs.

“If these talks break down, the administration is going to have to start doing more aggressive implementation of sanctions and things that, in the past, they likely decided were too aggressive or too dangerous,” Anthony Ruggiero, then a senior fellow at the Foundation for Defense of Democracies, told the Washington Examiner in May. “And they're going to have to move to that next level rapidly.”

Ruggiero, who joined the White House National Security Council’s Korea desk in July, said at the time that those “more aggressive” measures should include a plan to “start to interdict these vessels” at sea.