KYIV (Reuters) - Ukrainian President Volodymyr Zelenskiy said on Tuesday he wanted to negotiate an unconditional 30-day ceasefire face-to-face with Vladimir Putin at this week's talks in Istanbul because only the Russian leader could enact such a pause.

Ukraine's air force reported an overnight Russian attack involving more than 100 drones, as Russia's President Vladimir Putin rejected Ukrainian President Volodymyr Zelensky 's proposal of an immediate 30-day ceasefire.

Russia has called for direct negotiations with Ukraine in Istanbul, but Ukraine’s European allies say Putin needs to agree to a ceasefire first.

The Ukrainian leader had responded guardedly earlier on Sunday after the Russian president, in a night-time televised statement that coincided with prime time in the U.S., proposed that Ukraine and Russia hold direct talks in Istanbul next Thursday,

The EU is preparing new sanctions on Russia despite a potential meeting between Vladimir Putin and Volodymyr Zelenskyy on Thursday, three sources told CNBC.

This is the moment Vladimir Putin called Western leaders ‘morons’ after he was threatened with new sanctions. Key European leaders warned that Russia will face the sanctions if Putin fails to agree to a 30-day ceasefire and attend peace talks in Turkey on Thursday.

NBC News' Keir Simmons reports on the world leaders present at Russia's parade to mark the end of World War II. Brazilian President Lula also weighs in on the Russia-Ukraine war.