Russia and Ukraine have been negotiating with Turkey for two months an agreement on the safety of navigation in the Black Sea and reached a text that was to be announced by Ankara but Kiev suddenly pulled out, four sources with knowledge of the matter told Reuters.

The negotiations were brokered by Turkey at the request of the United Nations, according to the sources who spoke to Reuters on condition of anonymity because of the sensitivity of the matter. An agreement on the security of merchant ships in the Black Sea was reached in March and, although Ukraine did not want to formally sign it, it agreed to be announced by Turkish President Recep Tayyip Erdogan on March 30, ahead of crucial municipal elections.

“At the last minute, Ukraine suddenly pulled out and the deal collapsed,” said one of the sources.

Three other persons confirmed this version of events. Russia, Ukraine and Turkey declined to comment.

It is currently unclear why Ukraine backed out. The Reuters sources said they did not know what led to that decision.

Ukrainian President Volodymyr Zelensky said in February that without new US military aid Ukraine would not be able to defend the Black Sea “corridor” that runs close to Romania and Bulgaria.

Asked for comment, UN spokesman Stefan Dujarric said: “We remain hopeful that freedom of navigation in the Black Sea will prevail.”

The text of the agreement, a copy of which was obtained by Reuters, stated that Turkey had reached agreements with Ukraine and Russia to guarantee the free and safe passage of merchant vessels in the Black Sea, based on the Montreux Convention on the status of the Bosphorus Straits and the Dardanelles. Moscow and Kiev would offer security guarantees to merchant ships and undertake not to attack, seize or search them if they were carrying empty cargo or had declared civilian cargo. Warranties do not apply to warships and merchant vessels carrying military supplies, with some exceptions.

Turkey and the UN had brokered the Black Sea Grain Initiative, an agreement reached in July 2022 that allowed the safe export of nearly 33 million metric tons of grain from Ukraine. Russia pulled out of the deal in July 2023, protesting the obstacles facing its own food and fertilizer exports.