Russia resumed its assault on the last Ukrainian defenders holed up in a giant steel works in Mariupol on Saturday, days after Moscow declared victory in the southern city and said its forces did not need to take the plant.

Ukrainian President Volodymyr Zelenskyy said his country’s army was not ready to launch a military operation to restore access to the besieged city of Mariupol.

He said Saturday had been “one of the hardest days” yet for Ukrainian forces trapped in the port city, adding that Kyiv had offered Moscow every possible kind of exchange deal to secure their release.

Zelenskyy also repeated his warning that Ukraine would break off talks if Russia killed the remaining Ukrainian soldiers: “If our men are killed in Mariupol and if these pseudo-referendums are organized in the (southern) region of Kherson, then Ukraine will withdraw from any negotiation process.”

Zelenskyy also said eight people had been killed and 18 wounded in Russian strikes on Odesa on Saturday, updating an earlier death toll.