(Bloomberg) -- The drilling chief at Ukraine’s state-owned natural gas company urged Halliburton Co. and other oilfield contractors to cease operations in Russia to help starve that nation’s military of cash.

Russian President Vladimir Putin’s war machine is funded by proceeds from oil and gas exports, Oleg Tolmachev, head of production at Naftogaz, wrote in an open letter on Monday. Tolmachev, who was writing in his individual capacity and not on behalf of his employer, went to work for Naftogaz 13 months ago after more than two decades in U.S. shale fields. 

“Please terminate your business in Russia immediately and shut down your offices in Russian Federation,” he wrote. “My employees and their families in Kharkiv, Donetsk, Lugansk, and Poltava regions are getting killed and wounded by military forces of Russian Federation.”

Emails requesting comments from Halliburton, Schlumberger and Weatherford International Plc weren’t immediately returned.    

©2022 Bloomberg L.P.