UN Secretary-General Antonio Guterres on Wednesday hailed what he called "substantive progress" in ensuring the export of Ukrainian food products through the Black Sea.

"Today in Istanbul, we have seen a critical step forward to ensuring the safe and secure export of Ukrainian food products through the Black Sea," he told reporters at the UN Headquarters in New York. "In a world darkened by global crises, today, at last, we have a ray of hope -- a ray of hope to ease human suffering and alleviate hunger around the world, a ray of hope to support developing countries and the most vulnerable people, a ray of hope to bring a measure of much-needed stability to the global food system."

More technical work will be needed to materialize today's progress. But the momentum is clear. In the end, the aim of all parties is not just an agreement between Russia and Ukraine, but an agreement for the world, he said.

He thanked the Turkish government for its outstanding efforts to convene the talks and its critical role going forward. He thanked Russian and Ukrainian officials for their constructive engagement.

"The United Nations pledges to do our full part to support the follow-up," he said. "Today is an important and substantive step, a step on the way to a comprehensive agreement. We must also do more for struggling people and developing countries getting pummeled by a food, energy and financial crisis not of their making. We must do more to help all those living on the margins around the world -- countries on the brink of bankruptcy, families on the edge of famine."

There was very substantive progress and a broad agreement in the Istanbul talks, said Guterres.

There was substantive agreement on many aspects, mainly the questions related to the mechanisms of control, to the system of coordination, and to demining, he said.

"But of course, this was a first meeting. The progress was extremely encouraging. We hope that now the delegations are coming back to their capitals, and we hope that the next steps will allow us to come to a formal agreement," he said.

The UN chief would not predict how soon a final agreement will be reached.

"We are hoping that we'll be able to reconvene very soon -- I'm sure next week -- and hopefully we'll be able to have a final agreement. But as I said, we still need a lot of goodwill and commitment by all parties. They have shown it. I'm encouraged. I'm optimistic. But it's not yet fully done."

The United Nations will be together with Russia, Ukraine and Turkey in making sure that the next steps of coordination, of control, of the implementation, are done effectively. The United Nations is fully engaged in that common effort, he said.

The progress in the Istanbul talks is an extremely relevant step in relation to addressing the food crisis, together with the efforts in relation to the access of Russian food and fertilizers to the global markets, he said. "But I do not see immediately the perspective of a peace agreement. I think in any case, this demonstrated that the parties are able to have a constructive dialogue. And this is, of course, very good news. But for peace, we still have a long way to go."

The hopeful news from Istanbul shows the importance of dialogue, said Guterres. "Let us take inspiration from that ray of hope to help light a way to a desperately needed negotiated solution for peace in line with the UN Charter and international law."