In brief: Elon Musk has denied claims that he spoke to Russian president Vladimir Putin before posting a controversial tweet about how to end the war in Ukraine. The report claims that the pair discussed Russia's potential use of a nuclear weapon if Ukraine retook territory in Crimea.

Ian Bremmer, political scientist and president of political risk research firm Eurasia Group, said in his newsletter that Musk had a "direct conversation" with Putin about the war. Bremmer said it was Musk himself who told him about the conversation.

According to Bremmer's letter, Putin told Musk he was prepared to negotiate an end to hostilities but only if certain conditions were met: Crimea, which was annexed in 2014, remained Russian; Ukraine recognized Russia's annexation of Luhansk, Donetsk, Kherson, and Zaporizhzhia; and Ukraine remained neutral.

Putin allegedly told Musk that these goals would be achieved "no matter what," even if it means the use of a nuclear strike if Ukraine tried to take back Crimea. Bremmer wrote that Musk told him "everything needed to be done to avoid that outcome."

Musk tweeted a poll last week to gauge reaction to his Ukraine peace plan that essentially covered all of Putin's requirements, adding that the sham referendums in the annexed regions be redone under UN supervision. Just under 60% of the 2.7 million votes disagreed with the proposal. The Tesla boss later warned of the danger of Russia using nuclear weapons.

Musk has denied Bremmer's claims. He says the last time he spoke to Putin was 18 months ago, and the only thing they talked about was space.

Following the denial, Bremmer wrote: "Elon Musk told me he had spoken with Putin and the Kremlin directly about Ukraine. he also told me what the kremlin's red lines were."

"I have been writing my weekly newsletter on geopolitics for 24 yrs. I write honestly without fear or favor and this week's update was no different […] i've long admired musk as a unique and world-changing entrepreneur, which i've said publicly. he's not a geopolitics expert."

Musk's proposal was welcomed by the Kremlin but criticized by Ukraine and several politicians. Ukraine's outgoing ambassador to Germany, Andriy Melnyk, replied with "F**k off is my very diplomatic reply to you." He noted that no Ukrainian will ever buy "your f…ing tesla crap."

A few days after tweeting his Ukraine peace plan, Musk suggested a way to solve the Taiwan/China crisis through a "reasonably palatable" arrangement between the two nations. It was praised by Beijing but, unsurprisingly, slammed by the island country.