TALLINN, Estonia (AP) — The discussions have taken place in an ornate Kremlin hall, on the polished marble of St. Peter’s Basilica and in a famously contentious session in the Oval Office of the White House.

Ukraine's Air Force lost a Su-27 fighter jet during a Russian aerial attack on April 28. The aircraft was conducting a combat mission, supporting ground troops. The loss follows the earlier downing of the second F-16 fighter jet, which reportedly occurred in the Russia-bordering northeastern region of Sumy on April 16.