Dmitry Kozak, a long-time ally of President Vladimir Putin, has resigned from his position as deputy chief of staff at the Kremlin, as confirmed by spokesperson Dmitry Peskov on Thursday.

Kozak’s resignation comes in the wake of a New York Times report from last month, which suggested he had fallen out of favor with Putin due to his objections regarding the invasion of Ukraine in 2022.

Previously regarded as a significant power player within the Kremlin, Kozak has since adopted a more subdued role and is said to have transferred important tasks to Sergei Kiriyenko, the prominent first deputy chief of staff.

According to the business news outlet RBC, which reported the resignation on Wednesday, Kozak submitted his resignation over the weekend and is considering opportunities in the private sector.

The Kremlin later acknowledged Kozak’s resignation, with Peskov stating that he chose to leave for “personal reasons” during a press briefing on Thursday, though he did not elaborate further.

Later that day, an executive order officially relieving Kozak of his duties was made available on the Kremlin’s website.

Kozak, who hails from the Kirovohrad region of Ukraine during the Soviet era, held various legal positions in St. Petersburg throughout the 1990s, coinciding with Putin’s time in the mayor’s office. He entered federal government service in 1999 and joined Putin in the Kremlin after Putin’s presidential election the following year.