After talks with Russia in Istanbul collapsed in March 2022, Ukraine continued to contact the Russian side through secret channels and achieved some success, Defense Minister of Ukraine Rustem Umerov said in an interview with The Washington Post.

"In the secret 2022 talks, there were several negotiating tracks through international partners. These efforts resulted in a 'humanitarian corridor' that allowed 400,000 people to escape Russian-occupied territory, exchanges of prisoners of war, political prisoners and wounded soldiers, and a grain-export deal that allowed Ukraine to resume shipments through the Black Sea," the publication said citing the minister.

The United States "was always aware" of these contacts, Umerov said, "because we were always consulting on every track."

U.S. officials confirmed that the secret talks took place in 2022, when Russia was publicly threatening to use tactical nuclear weapons.