Volodymyr Zelensky, in the next phase of talks to end the war in Ukraine, intends to draw a red line at the most contentious issue on the table: the Russian demand for Ukraine’s sovereign territory. As long as he remains the nation’s president, Zelensky will not agree to give up land in exchange for peace, Ukraine’s chief negotiator, Andriy Yermak, told me today in an exclusive interview.

“Not a single sane person today would sign a document to give up territory,” said Yermak, who has served as Zelensky’s chief of staff, lead negotiator, and closest aide throughout the full-scale war with Russia.

“As long as Zelensky is president, no one should count on us giving up territory. He will not sign away territory,” he told me by telephone from Kyiv. “The constitution prohibits this. Nobody can do that unless they want to go against the Ukrainian constitution and the Ukrainian people.”

On the question of land, Ukraine is prepared to discuss only where the line should be drawn to demarcate what the warring sides control. “All we can realistically talk about right now is really to define the line of contact,” Yermak said. “And that’s what we need to do.”

The Ukrainian position for the next round of talks, which Yermak laid out for the first time, will sharply constrain the space available for negotiators to reach a peace deal. Russia has shown no willingness to back away from its demand for Ukrainian territory, including parts of the country that Russian forces do not control. Even though negotiators have made progress toward an agreement in recent days, they remain far apart on the crucial question of territory, where the Russian and Ukrainian positions appear difficult, if not impossible, to reconcile.

Russia first seized parts of Ukraine in 2014, when it annexed Crimea in a swift and nearly bloodless land grab. In September 2022, during the first year of the full-scale invasion, Russian President Vladimir Putin claimed that four additional regions of southern and eastern Ukraine—Donetsk, Luhansk, Zaporizhzhia, and Kherson, comprising about 15 percent of the country’s territory—would “forever” be a part of Russia. The Kremlin then staged a referendum to approve the annexation of these regions and to define them as Russian territory under the Russian constitution, making it politically difficult for Putin to reverse his territorial claims.

The problem for Putin is that Ukraine still controls large parts of Donetsk, Kherson, and Zaporizhzhia. The Russian military has been fighting for nearly four years to seize all of those regions by force, with the most intense battles centered around Donetsk, part of Ukraine’s industrial heartland. Ukrainian forces have dug in to defend the areas of Donetsk they still control, building fortifications and fielding weapons that have managed to hold back the invaders. Putin has tried to gain control of that territory through negotiations, offering to stop the Russian onslaught if Ukraine gives it up without a fight.

Read: Why Trump Pushed for Peace—Again

Yermak called me today during a holiday lull following an intense week of negotiations. Envoys from the United States and Ukraine gathered in Geneva on Sunday to rework an American peace proposal that was heavily weighted in Russia’s favor. The plan included a demand for Ukraine to cede territory in Donetsk, where the Russian military has made slow and plodding advances in recent months at an enormous cost in casualties.

At the conclusion of the talks in Geneva, where Secretary of State Marco Rubio represented the U.S. alongside President Donald Trump’s son-in-law Jared Kushner and his special envoy, Steve Witkoff, the negotiators stripped out the most onerous Russian demands on Ukraine.

They continued to work on the deal on Tuesday in Abu Dhabi, resulting in a proposal that “does not contradict our interests and takes into account our red lines,” Yermak said. Only a few questions were set aside in the negotiations for the presidents of Ukraine and the U.S. to decide, he added, including all points related to Ukrainian territory.

Zelensky’s team requested a meeting with Trump this weekend to discuss the proposal. But the president decided to first send Witkoff to Moscow to discuss the revised terms of the peace agreement with the Kremlin. Russian Foreign Minister Sergei Lavrov signaled at a press conference on Tuesday that Moscow would stick firmly to its core demands, which have long included its territorial claim on Donetsk and other regions of eastern and southern Ukraine.

Trump discussed the Kremlin’s conditions for peace in August during his summit in Alaska with Putin. The Russian and American leaders had planned in October to meet again in Budapest in hopes of advancing the peace process. But Trump scrapped those plans after Lavrov staked out an inflexible position during a preparatory call with Rubio, who then advised the White House not to proceed with another presidential summit.

The peace talks resumed in earnest only this month, just as a massive corruption scandal weakened Zelensky’s standing among the people of Ukraine and his allies in the West. A 15-month investigation, unveiled on November 10 by the National Anti-Corruption Bureau of Ukraine, accused several senior government officials and one of Zelensky’s former business partners of extorting and laundering about $100 million in bribes.

Investigators have not directly implicated Zelensky or Yermak in the case. But calls for Yermak’s resignation have intensified amid the scandal. “Zelensky needs to clean house,” a senior European diplomat told me earlier this month. “And he should start with Yermak.”

In our interview, Yermak responded at length for the first time to the investigation and the resulting calls for him to step aside. “The pressure is enormous,” he told me. “The case is fairly loud, and there needs to be an objective and independent investigation without political influence.”

By appointing him to lead Ukraine’s negotiating team despite the scandal, Zelensky made clear to the people of Ukraine that Yermak continues to enjoy his trust, he said. The people of Ukraine “see that I have been beside the president all these years during all the most difficult, tragic, and dangerous moments,” Yermak said. “He trusted me with these negotiations that will decide the fate of our country. And if people support the president, that should answer all their questions.”