Sen. Bob Menendez (D-N.J.) is pressing Energy Secretary Rick Perry for details on the trip he led to Ukrainian President Volodymyr Zelensky's inauguration in May that was cited in a whistleblower complaint against President Donald Trump.

The letter sent today was similar to a request for information Menendez sent to Vice President Mike Pence, and seeks to know who asked Perry to lead the delegation and for what reason, and whether Trump asked him to convey a desire for assistance in investigating domestic political opponents.

Menendez also asked whether Perry ever discussed Ukrainian corruption with officials during the trip, and if there were any records between Trump and foreign leaders stored in a highly classified electronic system.

"Given your role as the leader of the official United States delegation to the inauguration, and the White House’s recent release of evidence that President Trump requested that Ukraine’s government investigate his domestic political opponent, your insight into the U.S. delegation’s trip is of particular interest to the Senate Foreign Relations Committee,"Menendez wrote.

A DOE spokesperson was not immediately available for comment.

Menendez requested a response to the letter by Oct. 4.