The US announced partial sanctions against the Myanmar junta’s most lucrative state-owned enterprise, one of Washington’s most significant moves yet to curtail the military regime’s access to easy cashflow to buy weapons.

The curbs by the US on Myanma Oil and Gas Enterprise, or MOGE, prohibits Americans from the provision, exportation, or re-exportation of financial services, directly or indirectly, to or for the benefit of the company. It will come into effect on Dec. 15, the Department of Treasury’s Office of Foreign Assets Control said in a statement.

“MOGE provides hundreds of millions of dollars in foreign revenues every year to the military regime’s coffers, which the regime uses to purchase weapons and military material from abroad,” Secretary of State Antony Blinken said in a statement. “Through the issuance of a financial services directive against MOGE, the United States seeks to disrupt the regime’s access to the U.S. financial system and curtail its ability to perpetrate atrocities.”  

Major General Zaw Min Tun, lead spokesman for the ruling State Administration Council, didn’t answer calls seeking comment.

The sanctions follow repeated calls from rights groups and the military’s opponents in Myanmar to do so since the regime seized power in a coup nearly three years ago. Since then, violence has escalated as ethnic armed groups ramp up attacks against a regime seen losing ground across the country of 55 million people.

Blinken said the US is also designating three entities and five individuals who have supported the regime’s perpetration of human rights abuses, and is coordinating with Canada and the United Kingdom to align sanctions. 

“Today’s designations close avenues for sanctions evasion and strengthen our efforts to impose costs and promote accountability for the regime’s atrocities,” he said.

Bloomberg News reported in March that the US was weighing sanctions against MOGE at a time companies from allies Thailand and South Korea had interests in energy projects in the Southeast Asian nation. The US was also concerned that sanctions could prompt China to fill the void and exert greater economic influence on Myanmar, according to people with direct knowledge of the matter.

“The US should continue to target the junta’s sources of revenue through full sanctions on MOGE that would freeze its assets and block all trade with it, including from the international oil field service companies that are supporting the maintenance and expansion of gas fields which finance atrocities,” said Yadanar Maung, a spokeswoman for Justice for Myanmar.

MOGE’s prized assets include the Yadana field, which is operated by Thailand’s PTT Exploration & Production Pcl. Chevron Corp. reached deal to sell its 41.1% working interest in the project in February to Canadian firm MTI Energy after TotalEnergies SE earlier exited the project, according to media reports. 

PTT Exploration & Production immediately didn’t respond to request for comments on the US sanctions. 

Imports from Myanmar last year accounted for 16% of Thailand’s total natural gas supply, which makes up more than half of the country’s power generation mix, according to the Thai Ministry of Energy.