The United Nations, Turkey and Ukraine agreed Tuesday to pause shipments of grain through the Black Sea corridor on Wednesday, after Russia warned the security of the route had become "unacceptable."

Russia recently withdrew from a deal, brokered by the U.N. and Turkey, to ensure the shipment of grain via Ukraine's Black Sea ports needed in particular to feed vulnerable countries in places like North Africa and the Middle East. The three remaining parties in the initiative have continued to send ships through the route while informing Moscow of vessel movements.

The Joint Coordination Centre (JCC) in Istanbul, set up to implement the Black Sea deal, said in a statement that the three delegations had agreed "not to plan any movement of vessels in the Black Sea Grain Initiative" on Wednesday and suspended a vessel inspection process, citing "issues related to fumigated cargo."

The announcement came after Russia's defense ministry on Monday said the security situation along the corridor had become "unacceptable," claiming "the Ukrainian government and the top brass of the Ukrainian armed forces are using it for combat actions against the Russian Federation."

The U.N. has disputed Russia's claims about Ukraine's attack: Martin Griffiths, the U.N.’s humanitarian chief, said at a meeting of the U.N. Security Council on Monday that no ships were in the corridor at the time the attack on Russia's navy took place.

The JCC had sent a prior statement earlier in the day on plans to try to "resume full participation" in the deal after Moscow's withdrawal and for three vessels Tuesday to begin journeys to Germany, Libya and Morocco.

The U.N. Secretariat at the Joint Coordination Centre also stressed that movements through the corridor since Russia suspended its participation are "a temporary and extraordinary measure."

Russian President Vladimir Putin, meanwhile, held a call with his Turkish counterpart Recep Tayyip Erdoğan on Tuesday, during which he reiterated Moscow's claims about Ukrainian security threats and false accusations that the grain deal had mainly been used to benefit rich nations, according to the Kremlin.