Ukrainian President Volodymyr Zelenskyy called on Tuesday for steps to ensure Russia does not turn the Black Sea into a "dead zone" for shipping after Moscow quit a deal allowing safe Ukrainian grain exports.

On his first trip to Romania since Russia's invasion, Zelenskyy said after talks with President Klaus Iohannis that he had heard "good news" on artillery and air defense supplies from the NATO and European Union member state, but gave no details.

He told a joint press conference with Iohannis that Romania would help train Ukrainian pilots how to fly F-16 jets, signed a bilateral declaration on security and economic cooperation, and hailed the importance of Ukraine's ties with its neighbor.

"[The] Ukraine-Romania partnership is a factor of stability for Europe and beyond," Zelenskyy wrote on X, formerly known as Twitter. "Romania is a friend who came to our help on our darkest day and whose support gets stronger with time."

Underlining Romania's growing importance for Ukraine, Zelenskyy said a "corridor" would be soon be established to take Ukrainian grain to Romania via Moldova.

Kyiv has relied heavily on an export route along the River Danube that takes its grain to the world via the Romanian port of Constanta since Moscow quit the Black Sea safe-passage deal in July, but Russia often attacks Ukraine's river ports.

"We must do everything possible to prevent Russia from turning any part of the Black Sea and the Danube region into a dead zone for normal navigation," Zelenskyy said.

Referring to the southern Ukrainian region that includes Ukraine's two main Danube River ports, he said: "We are working with different partners to strengthen our air defense both in the entire country and in the Odesa region."

Food production and exports were vital for Ukraine's economy before Russia's full-scale invasion in February 2022, and Kyiv began seeking alternative shipping routes after Russia enforced a de facto blockade of Ukraine's Black Sea ports during the war.

Iohannis said 27 million tons of Ukrainian farm goods had already exported from Romanian ports. Zelenskyy, whose country is a major global grain grower and exporter, underlined the importance of getting Ukrainian grain to the world.

"Together, Ukraine and Romania are important donors for security, in particular, food security," he said.

Romania, which shares a 400-mile border with Ukraine, has detected several drone fragments falling on its territory as Russia attacked Ukrainian port infrastructure on the other side of the Danube.

Defense officials in Bucharest told Reuters last month that the Romanian military was moving air defenses closer to Danube villages and adding more observation posts to the area.

Romania also said this summer it was considering opening a regional training hub for F-16 pilots which would ultimately be available to its NATO allies and partners, including Ukraine.

Confirming that plan would go ahead, Zelenskyy said: "We discussed with President Klaus Iohannis how to speed up this training and agreed that Ukrainian pilots will be included in the first wave of training."