KYIV – Russia launched 10 Shahed and decoy drones at Ukraine in nighttime attacks, the Ukrainian air force said Tuesday, in the smallest drone bombardment this year as the warring countries prepare for possible peace talks in Turkey.

The Kremlin hasn’t directly responded to Ukrainian President Volodymyr Zelenskyy’s challenge for Russian leader Vladimir Putin to meet him in person at the negotiations in Istanbul on Thursday.

Zelenskyy will not be meeting with any Russian officials in Istanbul other than Putin, Mykhailo Podolyak, an adviser to Zelenskyy, said Tuesday on a YouTube show run by prominent Russian journalists in exile.

Lower-level talks would amount to simply “dragging out” any peace process, Podolyak said. European leaders have recently accused Putin of dragging his feet in peace efforts while he attempts to press his bigger army’s battlefield initiative and capture more Ukrainian land.

Russia effectively rejected an unconditional 30-day ceasefire demanded by Ukraine and Western European leaders from Monday, when it fired more than 100 drones at Ukraine. Putin instead offered direct peace talks with Ukraine in Istanbul on Thursday. Kremlin spokesman Dmitry Peskov insisted a Russian delegation would be in Istanbul without preconditions.

Both sides are preparing a spring-summer campaign on the battlefield, where a war of attrition has killed tens of thousands of soldiers on both sides along the roughly 1,000-kilometer (620-mile) front line.

The Institute for the Study of War, a Washington think tank, said Monday that Russia is “quickly replenishing front-line units with new recruits to maintain the battlefield initiative.”

Russia shunned the ceasefire proposal tabled by the U.S. and European leaders but offered direct talks with Ukraine.

Putin has repeatedly questioned the legitimacy of the Ukrainian government, especially Zelenskyy himself, saying his term expired last year. Under Ukraine’s constitution, it is illegal for the country to hold national elections while it’s under martial law, as it now is.

In a further complication, a Ukrainian decree from 2022 rules out negotiations with Putin.

But the U.S. has been applying stiff pressure on both sides since President Donald Trump came to power with a promise to end the war.

U.S. Secretary of State Marco Rubio spoke Monday with the top diplomats from the United Kingdom, France, Germany and Poland, who were meeting in London, to assess “the way forward for a ceasefire and path to peace in Ukraine,” spokesperson Tammy Bruce said.

Those European countries had pledged further sanctions on Russia if it didn’t comply with a full ceasefire that Ukraine had accepted from Monday, but they made no announcement of additional punitive measures.

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