Ukraine finally secured a deal aimed at restarting crucial Black Sea grain exports that have been crippled by Russia’s invasion. But getting them going won’t be easy.

Government officials from Kyiv and Moscow on Friday signed parallel agreements with Turkey and the United Nations at a meeting in Istanbul intended to help revive shipments from one of the world’s top wheat, corn and vegetable-oil exporters. That could be good news for a strained global food market and a Ukrainian economy that’s been wrecked by the war.

Yet even now with the accord, it will take time for traders and officials to kick-start the flows. Ukraine faces the task of clearing a pathway in mined seas, finding enough ships to carry the backlogged grain and re-routing trains and trucks that are now being used elsewhere. Getting insurance to cover operations is a challenge, too.