European Union member states Poland, Hungary and Slovakia have imposed import bans to protect their markets from an influx of cheaper supply following the Russian invasion of Ukraine, and Warsaw banned their transit through Poland at the weekend.
Polish Agriculture Minister Robert Telus said shipments of Ukrainian grain would be allowed to transit through Poland again, with shipments to be monitored and sealed. The deal is expected to go into effect at midnight on Friday.
Ukrainian First Deputy Prime Minister Yulia Svyrydenko said she was confident Ukrainian exporters would respect the terms of the deal agreed with Poland.
But she said the Black Sea grain deal was "under threat of being halted" as it is set to expire on May 18.
It is unclear whether it will be extended because Russia says a separate deal meant to ease its own agricultural and fertiliser exports has not been upheld.
It was not immediately clear how the other countries that have imposed import bans on Ukraine would react after the agreement in Warsaw, with Romania looking likely earlier on Tuesday to impose a similar ban.
Russian Foreign Minister Sergei Lavrov will discuss the Ukraine Black Sea grain export deal with UN Secretary-General Antonio Guterres in New York next week, just weeks before the pact could expire unless Russian demands regarding its exports are met.
Lavrov is due to chair two UN Security Council meetings as Russia holds the presidency of the 15-member body for April. Russian UN Ambassador Vassily Nebenzia said Lavrov and most of his delegation had received US visas to travel to New York.
He will also meet with Guterres, said Nebenzia. Russia has warned that the outlook for the deal allowing the safe wartime export of grain and fertilizer from Ukrainian Black Sea ports beyond May 18 is "not so great," Nebenzia told reporters off camera at the UN on Tuesday.
"I've no doubt this will be part of the discussions the Secretary-General has with the foreign minister," said UN spokesman Stephane Dujarric. "We continue to be determined to have this deal implemented fully as we are continuing with determination to work on the other part of the package, which is the facilitation of Russian grain and fertilizer. The stakes for this are very high. There are a lot of people around the world who depend on the food and the grain that's exported, who depend on fertilizer, and even if they don't depend on exactly those grains and fertilizer, they depend on the global price of food and fertilizer not to rise. I think it's important that everyone lives up to their responsibility."
"Nothing is moving, efforts are being made but unfortunately they are fruitless for us," Nebenzia said, referring to UN attempts to help facilitate Russia's own food and fertilizer exports despite broad Western sanctions imposed on Moscow over the invasion. "So far, no optimistic news ... We clearly said we want to see progress."
"It's a fact that we haven't had an inspection in two days, but that only redoubles our determination to ensure the full implementation of the deal and the MOU (memorandum of understanding)," said Dujarric.
The grain export deal was brokered by the United Nations and Turkey in July last year to help tackle a global food crisis that UN officials said had been worsened by Russia's invasion of Ukraine, the most deadly war in Europe since World War Two.
It was extended in November and then last month Russia only agreed to renew the deal for at least 60 days, half the intended period. Moscow said it would only consider a further extension if several demands in relation to its own exports were met.
To help persuade Russia to allow Ukraine to resume Black Sea grain exports, a separate three-year pact was also struck in July in which the UN agreed to help Russia export food and fertilizer.
Reuters