Russia and Ukraine have agreed to halt military strikes on vessels in the Black Sea and pause attacks on energy infrastructure, the United States has announced after talks with both sides in Saudi Arabia.

The White House said on Tuesday that Moscow and Kyiv had separately “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 agreements could represent the most significant step yet towards a broader ceasefire in the more than three-year Russia-Ukraine war, but it was not immediately clear when the partial truce would take effect or how it would be implemented.

Ukrainian President Volodymyr Zelenskyy said the entire agreement was effective immediately, but Moscow said the  Black Sea truce would only take effect once certain sanctions were lifted, including those targeting its state-owned agricultural bank, and that the pause in attacks on energy had been in force since last week.

“The US side considers that our agreements come into force after their announcement by the US side,” Zelenskyy told reporters at a news conference in Kyiv, adding that he did not expect Moscow to honour the agreement.

He hailed the partial truce as “the right steps”, claiming that Ukrainian and US officials had agreed a third party “from Europe or, for example, Turkiye” could oversee the sea ceasefire, while “someone from the Middle East” could monitor the moratorium on attacks on energy infrastructure.

Zelenskyy signalled that if Russia violated the agreement, he would seek more backing from the US. “If they violate, here is the evidence – we ask for sanctions, we ask for weapons,” he said.

The Kremlin said the Black Sea truce would “enter into force after the lifting of sanctions on Rosselkhozbank and other financial institutions involved in providing international trade operations in food and fertilisers.”

It also maintained that a 30-day pause on attacks on energy infrastructure had been in effect since March 18, when President Vladimir Putin first discussed it with US President Donald Trump. The agreement could, it said, be extended by mutual agreement.

Russian Foreign Minister Sergey Lavrov said his country did not trust Ukraine. “We will need clear guarantees,” he said. “And given the sad experience of agreements with just Kyiv, the guarantees can only be the result of an order from Washington to Zelenskyy and his team to do one thing and not the other.”

Reporting from Washington DC, Al Jazeera’s Alan Fisher said there was “still a lot of work to be done”.

“It’s clear that when Donald Trump said he had a plan to end the war within 24 hours after taking office, he perhaps misunderstood the differences between the two sides and just how much work would be needed,” Fisher said.

Russia seeks ‘guarantees’

The announcement came after US negotiators held separate talks with Russian and Ukrainian teams over several days in the Saudi capital, Riyadh.

During a 12-hour session on Monday, US and Russian officials discussed the possible resumption of the 2022 Black Sea Grain Initiative, an agreement that was supposed to allow Ukraine to ship millions of tonnes of grain and other food exports from its ports.

Moscow pulled out of the initiative, brokered by Turkiye and the United Nations, in 2023, accusing the West of failing to uphold its commitments to ease sanctions on Russia’s own exports of farm products and fertilisers.

The US said on Tuesday that it would “restore Russia’s access to the world market for agricultural and fertiliser exports, lower maritime insurance costs and enhance access to ports and payment systems for such transactions”.

Reporting from Moscow, Al Jazeera’s Dorsa Jabbari said Russia did not want a repeat of what happened with the 2022 agreement.

“They’re looking for guarantees, and it appears from the White House statement that the United States is willing to provide such guarantees,” she said.

Energy infrastructure

The focus of Tuesday’s deal is a much narrower one than a broad 30-day ceasefire that the US proposed to Russia in Saudi Arabia earlier this month.

Last week, after separate phone calls with Trump, both Putin and Zelenskyy agreed to a 30-day limited ceasefire, pledging not to attack energy infrastructure in each other’s territories.

However, there was confusion over what had been agreed, with the White House readout of the Trump-Putin call referring to “energy and infrastructure”, while the Kremlin referred only to “energy infrastructure”.

Ukraine, which called for the signing of a formal document, has accused Moscow of flouting the moratorium by continuing to target energy infrastructure, while also hitting civilian infrastructure, including a hospital in northeastern Sumy this week.

But the Kremlin insisted on Monday that Russia was still abiding by Putin’s promise to Trump despite Kyiv continuing to strike Russian energy facilities.

Over the past week, the Russian Defence Ministry said that Ukraine had attacked oil and gas targets, including the Valuika gas distribution station in the Belgorod region, the Glebovskoye gas condensate field in Crimea and Kavkazskaya oil depot in the Krasnodar region.

On Tuesday, the Kremlin said that Russian and US officials had agreed to work out “measures” aimed at implementing a 30-day ban on strikes on “Russian and Ukrainian energy facilities”.

“That was something that came out of previous negotiations,” said Al Jazeera’s Assed Baig in Kyiv. “The question is will this be implemented and how it will be implemented.”