With President Donald Trump pushing for a rapid end to the war that has killed tens of thousands of people, US negotiators shuttled separately over three days in the Saudi capital Riyadh between delegations from Ukraine and Russia.

In parallel statements, the White House said that each country "agreed to ensure safe navigation, eliminate the use of force and prevent the use of commercial vessels for military purposes in the Black Sea."

The United States said it would also look for ways to enforce a ban on strikes on energy infrastructure in the two countries.

The Kremlin meanwhile said the agreement to halt strikes on the Black Sea could come into force only after the lifting of restrictions on its agriculture sector.

It said Russia and the United States agreed that a 30-day energy truce ordered by Vladimir Putin last week applies to pipelines, power stations and refineries.

Ukrainian President Volodymyr Zelensky, who has turned to diplomacy after heavy pressure from Trump including a brief ban on US aid and intelligence sharing, said it was too early to tell if the agreements would work but that they were "the right steps."

Zelensky told a news conference in Kyiv that the talks also discussed bringing in third parties to oversee a future truce.

He said that Turkey, which has maintained ties with both sides, could monitor the situation on the Black Sea and that a Middle Eastern nation could supervise the energy agreement.

Trump spoke directly to Putin after taking office, ending the ostracization of him by the West since he ordered the invasion of Ukraine in 2022.

In the first concrete step by the United States toward Russia in return for the engagement, the White House said it would "help restore access to the world market" for Russian agricultural and fertilizer exports.

The United States never directly put sanctions on Russian agriculture but had restricted access to payment systems used for international transactions. 

The issue became a major talking point for Russia, which told countries in the developing world that US policies -- not the war itself -- were contributing to higher prices.

Moscow said the deal would "come into force" after the "lifting of sanctions restrictions" on the Russian Agricultural Bank and other "financial institutions involved in international trade of food," and only after they are reconnected to the SWIFT international payment system.

Zelensky, while saying he did not know full details of the US decision, voiced alarm.

"We believe that this is a weakening of the position and a weakening of sanctions," he said.

Ukrainian Defense Minister Rustem Umerov, who took part in the talks, said details on the Black Sea agreement were still being worked out.

He also warned that if Russian warships moved from the eastern part of the Black Sea then "Ukraine will have full right to exercise right to self-defense."

Ukraine earlier this month agreed to a US-proposed unconditional ceasefire, but Russia turned it down, with Kyiv accusing it of wanting to gain more battlefield advantage first.

Russian Foreign Minister Sergei Lavrov gave no sign that Moscow was closer to agreeing to a wider ceasefire and put a priority on shipping through the Black Sea.

A previous UN-brokered deal allowed millions of tonnes of grain and other food exports to be shipped safely from Ukraine's ports, but Russia had complained it was not beneficial for its trade.

Before the US announcement on agricultural exports, Lavrov accused Western countries of trying to "contain" Russia like "Napoleon and Hitler."

Zelensky said he was expecting to gain clarity from a coming summit in Paris on which countries might contribute forces to oversee possible truce agreements by sending peacekeepers to his country.

The Saudi talks came as both Russia and Ukraine escalate their attacks on the ground, with Kyiv saying its air defense units had downed 78 of 139 drones launched by Russia on Tuesday.  

In Ukraine's northeastern city of Sumy, officials said the toll from a Russian strike in a residential area a day earlier climbed to 101 wounded, including 23 children, with one adult and one child in serious condition.

Russia has advanced in some areas of the front for months and on Tuesday claimed to have captured two more villages in southern and eastern Ukraine.