Ukrainian Foreign Minister Dmytro Kuleba resigned on Wednesday, the highest-profile casualty so far of a major government reshuffle ordered by President Volodymyr Zelenskiy at a crucial juncture in the 30-month war against Russia.

After Zelenskiy, 43-year-old Kuleba was the best-known face of Ukraine overseas, meeting leaders around the world and lobbying for military and political support in fluent English.

More resignations and appointments are expected over the coming days after five ministers stepped down on Tuesday, in what a senior Zelenskiy ally cast as the start of a government “reset” ahead of the cold autumn and winter seasons.

Kuleba’s resignation letter was posted on Facebook by the speaker of parliament, Ruslan Stefanchuk.

Zelenskiy has said changes to the government were necessary to achieve the results required by Ukraine.

“Autumn will be extremely important for Ukraine. And our state institutions should be configured so that Ukraine achieves all the results that we need – for all of us,” he said on Tuesday.

Russian forces are advancing in the east of Ukraine while Ukrainian troops have made a bold incursion into Russia’s Kursk region.

Moscow has intensified drone and missile attacks in recent weeks and Kyiv launched a mass drone attack on Russia’s energy infrastructure over the weekend.

On Tuesday, at least 50 people, including soldiers, were killed by two missiles in the central Ukrainian town of Poltava in the deadliest single attack of the war this year.

Later this month Zelenskiy travels to the United States, where he hopes to present a “victory plan” to U.S. President Joe Biden, a key ally.

The Kremlin said that government changes in Ukraine would not affect a peace negotiation process in any way, although such talks appear a distant prospect with the two warring parties far apart in their objectives.

According to lawmaker Yaroslav Zheleznyak, parliamentary committees will consider the resignations and then parliament will vote on them in what is usually a formality. 

The new appointments are likely to be approved as soon as Thursday.

Zelenskiy is expected to nominate his candidate for a new foreign minister on Wednesday, with first deputy foreign minister Andrii Sybiha among the frontrunners.

On Tuesday, Strategic Industries Minister Oleksandr Kamyshin, Deputy Prime Minister Olha Stefanishyna and the justice, environment and reintegration ministers stepped down.

At least five portfolios have been vacant since ministers were fired or resigned earlier this year, including the important agriculture and infrastructure ministries.

Opposition lawmaker Iryna Herashchenko said: “It’s a government without ministers … an intellectual and personnel crisis that the authorities are closing their eyes to”.

She called for a government of national unity that would end the tight grip on the reins of power held by Zelenskiy’s political team.