KYIV, Ukraine: Andrii Yermak, Ukraine's powerful chief of staff and President Volodymyr Zelenskyy's lead negotiator in talks with the United States, has resigned following a search of his residence by anti-corruption investigators.

The search was a blow for the Ukrainian leader and risked disrupting his negotiating strategy at a time when Kyiv is under intense U.S. pressure to sign a peace deal nearly four years after Russia's full-scale invasion.

Yermak was Zelenskyy's trusted confidant, and the president had resisted persistent pressure to replace him.

Referring to the controversy over Yermak's extended stay at his side, Zelenskyy said Russia was waiting for Ukraine to make missteps that would upset the delicate, tense peace negotiations.

"We don't have a right to retreat or argue between ourselves. If we lose unity, we risk losing everything — ourselves, Ukraine, our future," Zelenskyy said. "We must unite, we must hold on. We have no other choice. We won't have another Ukraine."

"To preserve our internal strength, there must be no reason to be distracted by anything else except for the defense of Ukraine," he added. "I don't want anybody to be questioning Ukraine, and that's why we have today's decisions."

Zelenskyy also announced that he was "resetting" the presidential office. He said he would begin consultations to appoint a new chief of staff after Yermak resigned.

Yermak will no longer be a part of the Ukrainian delegation for the next round of negotiations with the U.S.

Head of Ukraine's armed forces, Andrii Hnatov, will now lead the delegation. The others in the team will be Andrii Sybiha, Ukraine's foreign minister, and Rustem Umerov, head of Ukraine's Security Council.

Two national anti-corruption agencies in Ukraine said their search was directed at Yermak. His spokesperson, Oleksii Tkachuk, said the agencies had not issued a notice of suspicion against Yermak, meaning he is not considered a suspect. Yermak was also not informed about the purpose of the searches, Tkachuk added.

Yermak confirmed that investigators searched his apartment inside the presidential compound in central Kyiv, an area with restricted public access. Media outlets reported that his office was also searched, though investigators did not comment on that claim.

It remained unclear where Zelenskyy or Yermak were during the early morning raid.

"The investigators are facing no obstacles," Yermak wrote on the messaging app Telegram. He said he was cooperating fully with them and that his lawyers were present.

In an interview with The Atlantic this week, Yermak said that as long as Zelenskyy is president, "no one should expect us to give up territory. He will not sign away land."

He said Ukraine is willing to discuss only the issue of which areas each side currently controls, based on the front-line positions.

"All we can realistically discuss right now is defining the line of contact," Yermak said.

Meanwhile, the National Anti-Corruption Bureau of Ukraine and the Specialized Anti-Corruption Prosecutor's Office are conducting a major investigation into a US$100 million energy-sector scandal involving senior Ukrainian officials.

It was unclear whether the searches were linked to that investigation. NABU spokesperson Anton Tatarnikov declined to comment, citing legal limits on sharing information about an active probe.

Anastasiia Radina, head of Ukraine's parliamentary anti-corruption committee, wrote on social media that Yermak's resignation was "Better late than never."