Vladimir Putin is assembling a heavyweight team with decades of experience in high-stakes negotiations to face off against US President Donald Trump’s representatives for a deal to end Russia’s war in Ukraine. They include Yuri Ushakov, his chief Kremlin foreign-policy adviser who has over 50 years of involvement in diplomacy, and his top spymaster, Sergei Naryshkin, who served with Putin in the Soviet KGB, according to people familiar with the situation. Kirill Dmitriev, a financier educated at Stanford and Harvard with ties to the Russian president’s own family, may play a key role as an unofficial back-channel with Trump’s negotiators, people familiar with the preparations said. Trump’s tea, by contrast, lacks the same depth of background on Ukraine and has little experience negotiating directly with Russia -...