WASHINGTON

Andriy Yermak, Ukrainian President Volodymyr Zelenskyy's chief of staff, met US Secretary of State Marco Rubio in Washington, DC on Wednesday to discuss the Ukraine war.

"We discussed the situation on the front lines and the urgent need to strengthen support for Ukraine’s air defense," Yermak said in a statement.

He said they also exchanged views on meetings with the Russian delegation in Istanbul, the course of negotiations, the upcoming prisoner exchange and the importance of bringing back all hostages and children abducted by Russia.

Istanbul hosted the second round of Russia-Ukraine talks on Monday after the first one on May 16. This time, the two sides agreed to exchange more prisoners of war -- focusing on the youngest and most severely wounded -- and return the bodies of 6,000 soldiers from each side.

"I emphasized that Ukraine has done everything possible to achieve peace and is ready for a ceasefire — but Russia refuses. That is why additional sanctions are necessary. We agreed to coordinate our next steps," he added.

A delegation of top Ukrainian officials, including Yermak, met Tuesday with US special representative for Ukraine and Russia Keith Kellogg and US Special Envoy Steve Witkoff.

Zelenskyy on Wednesday proposed an unconditional ceasefire with Russia until a meeting can be arranged with his Russian President Vladimir Putin, saying that Kyiv is prepared to meet "any day" in Istanbul, Switzerland or the Vatican.