WASHINGTON — The Trump administration has slapped sanctions on companies across the globe to punish illicit trade with nuclear-armed North Korea, yet Myanmar, which is suspected of acquiring ballistic missile systems from the pariah state, has escaped the full force of the “maximum pressure” campaign.

U.S. lawmakers of both parties say that’s a worrying gap in the U.S. sanctions regime. A recent United Nations report cites Myanmar’s “ongoing” arms relationship with North Korea — underscoring long-standing suspicions Myanmar has failed to sever those military ties as it has transitioned to democracy.

“I want Burma to succeed,” Republican Sen. Cory Gardner told The Associated Press, using the alternative name for Myanmar.

“I want its civilian leadership to succeed. But we can’t stand idly by and watch this military trade with the tyrant in North Korea,” said Gardner, who chairs a Senate panel on Asia.

Republican Rep. Ed Royce, chairman of the House Foreign Affairs Committee, also said Myanmar officials “buying arms and propping up the North Korean regime” must be sanctioned.

President Barack Obama lifted all sanctions on Myanmar in the fall of 2016 after Nobel laureate Aung San Suu Kyi was elected to power, ending five decades of army rule. That removed dozens of people and companies that had been blacklisted by the Treasury Department for human rights abuses and ties to the junta. But it also provided a reprieve to a handful of Myanmar companies and military officials accused of military trade with North Korea that violated U.N. Security Council resolutions.

After President Donald Trump took office, Myanmar’s main player in that trade, the Directorate for Defence Industries, was designated again, but this time under a weaker sanctions authority that restricts it from U.S. government contracts and export licensing. However, the other Myanmar companies and persons that used to be blacklisted have not been sanctioned again, and none has been put back on the Treasury Department’s list of Specially Designated Nationals. Such a designation bars them from holding any U.S. property, doing business with Americans and conducting transactions in the U.S. financial system.

Joseph DeThomas, a former senior State Department sanctions expert, said that for any reputable company it’s bad to be under any U.S. sanctions, but “nothing makes your life more miserable than having every bank in the world know you are on the SDN list.”

The U.N. report, recently made public, says the Directorate for Defence Industries maintains a “sophisticated global procurement network.” It also mentioned Soe Min Htike Co. Ltd and Excellence Mineral Manufacturing Co. Ltd, two Myanmar companies that were also once on the Treasury blacklist.

SDN listing is a tool that Trump has used extensively on North Korea in his “maximum pressure” campaign that he credits for North Korean leader Kim Jong Un’s recent offer of negotiations on “denuclearization.” Despite president’s surprise consent to a hold a summit with Kim by May, the administration says the campaign will continue until North Korea takes concrete action to end its nuclear program.

In the past year, the U.S. has blacklisted about 200 companies, banks, persons and ships based in North Korea, China, Singapore, Taiwan, Hong Kong, the Marshall Islands, Russia, Georgia, the United Arab Emirates and Vietnam. That has intensified North Korea’s economic isolation in support of U.N. sanctions that have cut deeply into the North’s export earnings.

Myanmar is still a potentially important source of funds for Pyongyang.

When it was under junta rule, it likely became the biggest customer in Asia for North Korean armaments, said Thomas Countryman, a former top State Department official on nonproliferation. He said that included a production facility for assembling short-range ballistic missiles.

As the U.S. normalized diplomatic relations, Myanmar took some positive steps to curtail its North Korea ties by stopping money transfers and restricting the activities of North Korean personnel. Myanmar also told U.S. officials it had cancelled North Korean contracts, Countryman said.

“There were several points at which we were assured that everything had stopped. Then it began to be clear that it hadn’t,” he said. That reflected differences between the civilian government, which wanted to sever the ties, and the powerful military, which did not, he said.

Myanmar is increasingly in Washington’s bad books again for a scorched-earth crackdown on Rohingya Muslims that the U.S. has called “ethnic cleansing.” The administration has already designated one military official. A bill approved by the Senate Foreign Relations Committee last month seeks sanctions on others responsible atrocities. The legislation would also require SDN listing for any Myanmar officials purchasing arms from North Korea.

“Myanmar ending its proliferation relationship with North Korea was supposed to be one of the first returns on U.S.-Burma engagement,” complained Democratic Sen. Ben Cardin, a co-sponsor of the bill. “Yet even as the United States has loosened and lessened sanctions on suspected Burmese entities, there are continued revelations of their business dealings with North Korea.”

The U.N. report cited an unidentified member state as saying that Myanmar had an “ongoing arms relationship” with the Korea Mining Development Trading Corporation, or KOMID, and “was expecting future shipments.” KOMID is the North’s primary arms dealer and main exporter of ballistic missiles and conventional weapons, and is blacklisted by both the U.S. and the U.N.

The report said Myanmar received ballistic missile systems, multiple rocket launchers and surface-to-air missiles, and noted that last year Myanmar expelled a North Korean diplomat for acting on behalf of KOMID — suggesting an enduring relationship, although the government had told the U.N. panel it had “no substantive bilateral relations” beyond normal diplomatic ties with North Korea.

The Treasury Department wouldn’t comment on further U.S. action other than to say that “no country, including Burma will get a pass on sanctionable activity with North Korea.”