KIEV (Reuters) – A senior Ukrainian security official offered to quit before President Volodymyr Zelenskiy began a visit to the United States this week, the president’s office said on Friday.

Oleksandr Danylyuk, the secretary of Ukraine’s National Security and Defense Council, gave no reason for his decision and will stay on until Zelenskiy decides whether to accept his resignation, it said in a statement.

The statement gave no indication that the resignation was connected with a telephone call between Zelenskiy and Donald Trump that is at the center of a formal impeachment inquiry into the U.S. president.

In the July 25 call, Trump asked Zelenskiy to investigate Joe Biden and his son Hunter, who worked for a Ukrainian gas company for several years, according to a summary of the conversation released by the White House.

Biden, a former vice president, is a leading contender in the Democratic race to take on Trump in the 2020 presidential election.

Trump’s administration also released a whistleblower’s complaint that questioned whether U.S. aid was held up until Ukraine showed it would act on Trump’s request.

Reuters could not immediately contact Danylyuk for comment. Earlier this week he told Reuters Ukraine did want not to be dragged into U.S. domestic politics.

Danylyuk is a former finance minister who oversaw the nationalization of PrivatBank, Ukraine’s largest lender, and his appointment to his security role in May sent a positive signal to investors gauging Zelenskiy’s reformist credentials.

Investors are also looking for Kiev to conclude a new loan agreement with the International Monetary Fund to help underpin economic stability, tackle reforms and fight corruption. An IMF delegation left Ukraine on Friday without finalizing an agreement.

Reporting by Matthias Williams and Ilya Zhegulev and Pavel Polityuk, Editing by Andrew Heavens and Timothy Heritage