Diplomatic efforts to end the war in Ukraine were stepping up on Monday, with Ukrainian and Russian negotiators set to talk again after both sides cited progress, even after Russia attacked a base near the Polish border and fighting raged elsewhere.

A barrage of Russian missiles hit Ukraine’s Yavoriv International Centre for Peacekeeping and Security, a base just 15 miles (25 km) from the Polish border that has previously hosted NATO military instructors, killing 35 people and wounding 134, a Ukrainian official said on Sunday.

Russia’s defence ministry said up to 180 “foreign mercenaries” and a large number of foreign weapons were destroyed. Reuters could not independently verify the casualties reported by either side.

Thousands of people have died since February 24, 2022, when Russian President Vladimir Putin launched what he called a special military operation to rid Ukraine of dangerous nationalists and Nazis.

The United States, which had watched Russia’s build-up on Ukraine’s borders with mounting alarm for weeks, says it was a premeditated, unjustified and unlawful “war of choice”.

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In a telephone call, U.S. President Joe Biden and France’s Emmanuel Macron underscored their commitment to holding Russia accountable for the invasion, the White House said.

According to Reuters, U.S. Secretary of State Antony Blinken and his Ukrainian counterpart, Dmytro Kuleba, also discussed diplomatic efforts to stop Russia’s invasion, the State Department said.

Hopes were boosted after Russia and Ukraine gave their most upbeat assessments after weekend negotiations.

“Russia is already beginning to talk constructively,” Ukrainian negotiator Mykhailo Podolyak said in a video online. “I think that we will achieve some results literally in a matter of days.”

A Russian delegate to the talks, Leonid Slutsky, was quoted by the RIA news agency as saying they had made significant progress and it was possible the delegations could soon reach draft agreements.

Ukraine said talks via video are due to start at 10:30 a.m. Kyiv time (0830 GMT). Neither side has said what they would cover. Three rounds of talks between the two sides in Belarus, most recently last Monday, had focused mainly on humanitarian issues.

Ukrainian President Volodymyr Zelenskiy said the countries’ delegations have been speaking daily by video link and a clear aim of his negotiators was to “do everything” to arrange for him to meet Putin.

“We must hold on. We must fight. And we will win,” Zelenskiy said in a late night video speech.

The Star