Talks in Saudi Arabia between delegations from the United States and Russia have again failed to produce a comprehensive ceasefire between Moscow and Kyiv.
However, in separate deals, Ukraine and Russia both agreed with the US to cement an informal truce already in place in the Black Sea.
The talks also provided more information on a plan, announced last week, that would see Ukraine and Russia stop attacking each other's energy infrastructure.
The US and its President Donald Trump are keen to see the war in Ukraine, which has raged for more than three years since Russia's full-scale invasion, end as soon as possible.
Saudi Arabia has hosted multiple talks over the past month between delegations from the US, Russia and Ukraine aimed at ending the conflict, although never with all three nations in the same room.
In statements released after the talks in Riyadh, the US said it had agreed with Russia and Ukraine to "ensure safe navigation, eliminate the use of force, and prevent the use of commercial vessels for military purposes in the Black Sea".
While the Black Sea has previously seen multiple attacks since Russia's full-scale invasion of Ukraine in February 2022, it has not been the centre of fighting for a long time.
Last week, in what had been hailed as a breakthrough, the US claimed Russia and Ukraine had agreed to stop attacking each other's energy infrastructure.
However, that development was clarified in a statement released by the White House after the talks in Riyadh on Tuesday, which said: "The United States and Russia agreed to develop measures for implementing President Trump's and President Putin's agreement to ban strikes against energy facilities of Russia and Ukraine."
It would suggest that, while there has been some progress, no deal is yet in place.
'A discussion about nothing'
While Tuesday's announcement about the Black Sea ceasefire was welcomed by some analysts as a concrete step towards peace, others argued there was already an "informal ceasefire" in place in the region.
"It's a quid pro quo situation [right now], in which Ukrainians don't attack Russian merchant ships and Russians do not attack Ukrainian merchants," Vlad Mykhnenko, a Professor of Geography and Political Economy at the University of Oxford, told the ABC.
"So there is an informal ceasefire already in place that seems to be holding up quite well. So this is just a discussion about nothing really."
Russia last year relocated most of its Black Sea naval fleet from Sevastopol, on the Crimean peninsula, to Novorossiysk.
Moscow's military annexed the Crimean peninsula in 2014, and the decision to move the ships to a port on the Russian mainland was considered a major win for Ukraine, which had managed to sink dozens of vessels with aerial attacks despite not having a navy.
[New map]Russian Foreign Minister Sergei Lavrov, in comments on state television, said his country could not trust Ukrainian President Volodymyr Zelenskyy.
"We will need clear guarantees. 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," Mr Lavrov said.
In a sign of how fraught the negotiations have been, Russia's foreign ministry issued a statement after the US sent theirs saying the Black Sea ceasefire wouldn't come into effect until multiple financial sanctions linked to trade were lifted.
Mr Zelenskyy told reporters in Kyiv that the latest deals were a step in the right direction.
"It is too early to say that it will work, but these were the right meetings, the right decisions, the right steps," he said.
"No one can accuse Ukraine of not moving towards sustainable peace after this."
Speaking to the media on Tuesday, President Donald Trump said the US would work with "other countries" to monitor the Black Sea ceasefire.
He said the US would be continuing "deep talks" with Russia and Ukraine.
"I would say it's going well, but it's a situation we should have never had to even think about," he said.
"There's tremendous animosity. There's a lot of hatred, as you can probably tell."
