ODESA, Ukraine >> President Volodymyr Zelenskyy visited one of Ukraine’s main Black Sea ports Friday, a week after a deal was struck with Russia, Turkey and the United Nations to create safe corridors for ships to export grains that have been trapped in the country since the war began five months ago.

His visit to a port in the Odesa region comes as workers were seen preparing terminals for grain exports, which are relied on by millions of impoverished people worldwide facing hunger.

“The first vessel, the first ship is being loaded since the beginning of the war,” Zelenskyy said.

He said the export of grain will begin with the departure of several ships that were loaded but could not depart the Ukrainian ports after the Russian invasion.

“Our side is fully prepared. We sent all the signals to our partners — the U.N. and Turkey, and our military guarantees the security situation,” he said, adding “it is important for us that Ukraine remains the guarantor of global food security.”

The visits to the ports are part of a broader push by Ukraine to show the world they are nearly ready to export millions of tons of grains to the world again after last week’s breakthrough agreement.

The complexities of the agreement and concerns about the safety of shipping crews has set the deal off to a slow, cautious start. It’s been a week since it was signed, and no grains have yet left ports. But the sides are facing a ticking clock — the deal is only good for 120 days.

It comes a week after Russian missiles struck Odesa, throwing into question Moscow’s commitment to the deal signed only hours earlier. The sides agreed to facilitate the shipment of Ukrainian wheat and other grains from Black Sea routes blocked by five months of war, as well as fertilizer and food from Russia.

The goal over the next four months is to get some 20 million tons of grain out of three Ukrainian sea ports blocked since the Feb. 24 invasion. That provides time for about four to five large bulk carriers per day to transport grain from the ports to millions of impoverished people worldwide facing hunger.

“We are ready,” Ukraine’s minister of infrastructure, Oleksandr Kubrakov, told reporters at the port of Odesa on Friday.

But he said Ukraine is waiting on the U.N. to confirm the safe corridors that will be used by ships navigating the waters, which have been mined with explosives. In the meantime, a ship at the port of Chernomorsk was being loaded with grains, he said.

Martin Griffiths, the U.N. official who mediated the deal, said the first shipment of grains could depart Ukrainian ports as early as Friday but cautioned that work is still being done to finalize the exact coordinates of the safest routes, saying this must be “absolutely nailed down.”

Lloyd’s List, a global publisher of shipping news, noted Friday that while U.N. officials are pushing for the initial voyage this week to show progress in the deal, continued uncertainty on key details will likely prevent an immediate ramping-up of shipments.

“Until those logistical issues and detailed outlines of safeguarding procedures are disseminated, charters will not be agreed and insurers will not be underwriting shipments,” wrote Bridget Diakun and Richard Meade of Lloyd’s List.

They note, however, that U.N. agencies, such as the World Food Program, have already arranged to charter much of the grain for urgent humanitarian needs.

Getting wheat and other food out is critical to farmers in Ukraine, who are running out of storage capacity amid a new harvest. Those grains are vital to millions of people in Africa, parts of the Middle East and South Asia, who are already facing food shortages and, in some cases, famine.

Since the deal was signed a week ago, shipping companies have not rushed in because explosive mines are drifting in the waters, ship owners are assessing the risks and many still have questions over how the agreement will unfold.

Ukraine, Turkey and the U.N. have been keen to show the deal is in action since it was signed one week ago. Turkish Defense Minister Hulusi Akar told Al Jazeera on Thursday that “the deal has started in practice” and that the first ship leaving Ukraine with grains is expected to depart “very soon.”

Turkish Foreign Minister Mevlut Cavusoglu expressed similar optimism in a press briefing, framing the deal as a significant step forward between the warring sides.

“This is not just a step being taken to lift the hurdles in front of the export of food. If implemented successfully, it will be a serious confidence-building measure for both sides,” he said.

The deal stipulates that Russia and Ukraine will provide “maximum assurances” for ships that brave the journey through the Black Sea to the Ukrainian ports of Odesa, Chernomorsk and Yuzhny.

For ships heading to Ukraine’s three ports, smaller Ukrainian pilot boats will guide the vessels through approved corridors. The entire operation will be overseen by a Joint Coordination Center in Istanbul staffed by officials from Ukraine, Russia, Turkey and the United Nations.

Once ships reach port, they will be loaded with tens of thousands of tons of grains before departing back to the Bosphorus Strait, where they will be boarded to inspect them for weapons. There will likely be inspections for ships embarking to Ukraine as well.