UNITED NATIONS, United States, May 30, 2025 (AFP) - Hope is "just barely" alive in the negotiations between Russia and Ukraine, a senior UN official said Thursday, denouncing the recent "brutal surge in large-scale Russian attacks" against Ukraine.

UN Under-Secretary-General for Political Affairs Rosemary DiCarlo told the Security Council that the "cautious hope" she expressed a month ago has diminished in the face of recent aggressions.

"According to Ukrainian officials, with 355 drones, Monday's attack was the largest drone attack on Ukraine since the start of Russia's full-scale invasion," DiCarlo said, adding: "This topped the previous record from the night before."

Despite no declaration of a ceasefire, DiCarlo praised diplomatic efforts in Istanbul on May 16 when Ukrainian and Russian delegations met, saying "it is encouraging that the sides have reportedly agreed to continue the process."

"The massive wave of attacks over the weekend is a stark warning of how quickly this war can reach new destructive levels. Further escalation would not only aggravate the devastating toll on civilians but also endanger the already challenging peace efforts," DiCarlo said.

"The hope that the parties will be able to sit down and negotiate is still alive, but just barely."

- 'Just peace' -

Relaunched in mid-February by Washington, talks aimed at reaching a diplomatic settlement to the conflict that erupted with Russia's full-scale invasion in February 2022 have so far yielded no results.

John Kelley, acting US alternate representative, seemed to echo DiCarlo's frustration, insisting that prolonging the war was not in anyone's best interest.

"If Russia makes the wrong decision to continue this catastrophic war, the United States will have to consider stepping back from our negotiation efforts to end this conflict," he warned.

"Additional sanctions on Russia are still on the table."

DiCarlo insisted that "serious, demonstrable and good faith efforts are needed -- now -- to get back on the road that could lead to a just peace."

"A full, immediate and unconditional ceasefire is such an effort, if only an initial one," she said.

According to the UN, a "just peace" respects sovereignty and the territorial integrity of Ukraine.

The Kremlin said Thursday that it was awaiting Kyiv's response to its proposal for new talks in Istanbul next Monday.

Ukraine, which accuses Russia of buying time, seeks Moscow's conditions before any meeting, and is calling for sanctions against Moscow to be "expanded and strengthened."

"Russia is not signaling any genuine intention to stop its war," Ukrainian deputy ambassador Khrystyna Hayovyshy told the council.

"Therefore we see no alternative but intensified international pressure, political, military and economic," she said.

Russian ambassador Vassily Nebenzia rejected her accusations, instead accusing Kyiv of "attempting to prolong the war."

"No new anti-Russian sanctions, nor deliveries of weapons to Ukraine or any other hostile steps vis-a-vis Russia will be able to prevent the inevitable military defeat of the Zelensky regime," he insisted.

DiCarlo acknowledged that "a peace process will not be easy, and it will take time."

"But it must not wait," she insisted. "The people of Ukraine, especially, cannot wait."