Energy Department spokeswoman Shaylyn Hynes did not comment on whether Perry had sought to expand the board, but said he has “consistently called for the modernization and reform of Kiev's business and energy sector in an effort to create an environment that will incentivize Western companies to do business in Ukraine.”

A White House spokesman referred questions to DOE.

Trump has defended his calls for Ukraine to investigate the Bidens, maintaining he has an “obligation to look at corruption.” Text messages released on Thursday showed U.S. diplomats discussing how a potential summit between Zelensky and Trump would depend on Ukraine “getting to the bottom of what happened” in the 2016 U.S. election, which Trump maintains was marred by an unproven conspiracy against him by Democrats and foreign allies.

Perry, who POLITICO reported is expected to resign next month , attended Zelensky's May inauguration in Kiev in place of Vice President Mike Pence. In addition, he was one of the administration’s "three amigos" on Ukrainian policy, along with Kurt Volker, the U.S. special representative for the Ukraine conflict, and Gordon Sondland, the U.S. ambassador to the European Union, as Sondland described their relationship in a July broadcast interview.

In Ukraine and other Eastern European countries, the former Texas governor often played the role of U.S. energy pitchman. He helped deliver a deal to export U.S. coal to Ukraine, and he cemented a natural gas deal with Poland that would send supplies to Ukraine and help reduce its dependence on Russian fuel.

Among Perry's numerous visits with Zelenksy and other Ukraine officials in the past year was a dinner with Zelensky, Trump’s son-law-Jared Kushner and other officials in June, according to a government photo taken by the U.S. of the event. The two met again the following month with Polish government officials to sign the energy cooperation agreement, according to news releases.

Perry also attended the bilateral meeting with Zelenksy and Trump in New York on Sept. 25, a DOE spokesperson confirmed.

The message from Perry to Zelensky, according to one person familiar with the discussions, was: "You've got to take steps on your anti-corruption efforts.”

Perry also called for shaking up Naftogaz to help it cut its reliance on energy supplies from Russia and open itself up for more investment from the U.S., people familiar with the discussions told POLITICO.

Specifically, Perry pushed Naftogaz to expand its supervisory board — a three-person entity that now includes Amos Hochstein, a former Biden aide and State Department energy official currently working for the U.S. liquefied natural gas company Tellurian. The other two members are Bruno Lescoeur, a former executive in charge of international affairs at the French energy company Engie, and Clare Spottiswoode, director of London-based advisory Gas Strategies.

Perry “didn’t feel like the board of Naftogaz was sufficiently high level and connected to global energy companies, so he suggested that they expand the board and bring in new higher-level, industry-connected people on an international basis, including some Americans,” said a second person familiar with the discussions.

The names that Perry floated for potential new board members included Robert Bensh, a Houston oil executive currently with Pelicourt LLC, as well as Michael Bleyzer, head of a private equity firm based in Houston, the source familiar with the board discussions said.

Bensch, who advised DOE on technical matters involving Ukrainian energy, had not “formally” been offered a role on the board, said a person familiar with the matter who requested anonymity to discuss personnel issues. Bleyzer did not immediately reply to a message left with his firm.

Two clients of Trump’s personal lawyer Rudy Giuliani, Ukrainian-American Trump donors Lev Parnas and Igor Fruman, had met with Naftogaz earlier this year to pitch themselves as suppliers of U.S. natural gas, according to media reports.

“I may or may not know anything about it,” Giuliani told POLITICO when asked whether he knew about Perry’s efforts to install new people on the board.

Perry is scheduled to travel in Eastern Europe next week to follow up on a energy-cooperation agreement the U.S., Ukraine and Poland signed last month, according to an Energy Department news release.

On Friday evening, House Democrats issued their third subpoena this week for documents related to a whistleblower’s complaint about Trump’s interactions with Ukraine’s leader. A subpoena issued earlier in the day to Pence by the chairmen of the House Intelligence, Foreign Affairs and Oversight panels seeks records related to May 23 and July 10 meetings at the White House that Perry attended, as well as documents about the decision to send him to Zelensky’s inauguration instead of Pence.

House Democrats have also sent a subpoena to Giuliani asking for communications involving Perry.

Ben Schreckinger contributed to this report.