The vessel's departure on Monday from the Ukrainian port of Odessa for Lebanon via Turkey under a safe-passage deal has raised hopes of further such departures which could help ease a burgeoning global food crisis.
Turkey expects roughly one grain ship to leave Ukrainian ports each day as long as the safe-passage agreement holds, a senior Turkish official, who asked to remain anonymous, said on Tuesday.
The United Nations has warned of the risk of multiple famines this year because of the war in Ukraine.
Monday's sailing was made possible after Turkey and the United Nations brokered a grain and fertiliser export agreement between Russia and Ukraine last month - a rare diplomatic breakthrough in a conflict that has become a drawn-out war of attrition since Russian troops poured over the border on February 24.
Ukrainian President Volodymr Zelenskiy in his nightly address late on Monday called the ship's departure "the first positive signal", but warned it was too early to draw conclusions or predict how things would play out.
"We cannot have illusions that Russia will simply refrain from trying to disrupt Ukrainian exports," Zelenskiy said.
Ozcan Altunbulak, Turkey's representative at a co-ordination centre created to oversee the restart of Ukrainian grain exports, said on Tuesday the vessel, the Sierra Leone-flagged ship Razoni, was on track to anchor at Istanbul on Tuesday night.
The only issue so far was a slight delay caused by bad weather, he said.
The ship, which is carrying 26,527 tonnes of corn, was due to arrive in Istanbul at around midnight local time (7am Wednesday AEST).
It will then be inspected by Russian, Turkish, Ukrainian and UN officials under the terms of the safe-passage agreement before continuing its journey to the Lebanese port of Tripoli, its planned final destination.
There are other hurdles to overcome however before millions of tonnes of Ukrainian grain can leave, including clearing sea mines and creating a framework for vessels to safely enter the conflict zone and pick up cargoes.
Known as Europe's breadbasket, Ukraine hopes to export 20 million tonnes of grain held in silos, and 40 million tonnes from the harvest now under way, initially from Odessa and nearby Pivdennyi and Chornomorsk, to help clear the silos for the new crop.
Russia has called the Razoni's departure "very positive" news. It has denied responsibility for the food crisis, saying Western sanctions have slowed its exports.
Russia and Ukraine accuse each other of laying mines that now float around the Black Sea and represent a hazard to shipping.
After failing to seize the capital Kyiv early in the war, Russia has been aiming to capture the eastern Donbas region, comprising Donetsk and Luhansk, which were partially occupied by Russia-backed separatists before the invasion.
It also aims to capture more of the south, where it annexed Crimea from Ukraine in 2014.
Ukraine, which has launched a counteroffensive in the south, continues to ask the West to supply more long-range artillery as it tries to turn the tide in the conflict.
