Tesla billionaire Elon Musk has denied reports he talked directly with Vladimir Putin about nuclear weapons and a "peace deal" that would see Ukraine give up territory to Russia.
The claims were initially made by Ian Bremmer, the president of the Eurasia Group consulting company, in a newsletter to subscribers.
Later, Bremmer wrote on Twitter that "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."
Bremmer says he has been writing his weekly newsletter for 24 years "without fear or favour" and that while he admires Musk as an entrepreneur, "he's not a geopolitics expert".
Among the things Bremmer said Musk told him were that Putin was "prepared to negotiate" but only if Crimea - illegally annexed by the Kremlin in 2014 - remained part of Russia.
There were also apparent demands for Ukraine to be neutral, and recognise the four eastern Ukraine territories annexed by Russia in September also as part of Russia.
Bremmer said that Musk also revealed Putin had talked about the potential use of nuclear weapons in Ukraine and that he told the Russian leader "everything needed to be done to avoid that outcome."
How has Elon Musk responded to the newsletter claims?
Responding to the claims made in the newsletter, SpaceX founder Elon Musk said the story wasn't true.
"I have only spoken to Putin once and that was about 18 months ago. The subject matter was space," he wrote on Twitter - a platform he is apparently going to buy.
Musk later wrote that "nobody should trust Bremmer".
Elon Musk found himself in the middle of another Ukraine controversy just last week, after posting a series of Tweets about Russia's invasion of Ukraine.
Ukraine's President Volodymyr Zelenskyy and Foreign Minister Dmytro Kuleba are among the most prominent politicians who responded to the online comments.
Musk tweeted about the conflict to his 107.7 million followers, telling them first that to achieve peace between Ukraine and Russia there should be a "redo" of what he labelled as "elections" -- referring to the sham referendums -- "under UN supervision" in four areas of eastern Ukraine illegally annexed by Russia.
Musk said "Russia leaves" those areas "if that is the will of the people".
He also said that Crimea, illegally annexed by Russia in 2014, should become "formally part of Russia, as it has been since 1783 (until Khrushchev's mistake)", referencing the 1954 decree issued by then-Soviet premier Nikita Khrushchev to transfer responsibility for Crimea to the Ukrainian Soviet Socialist Republic.
The line about Crimea being part of Ukraine was "Krushchev's mistake" has long been a Kremlin talking point.
Crimea held a referendum in 1991 on its independence as a distinct socialist republic within the Soviet Union, largely favouring being a part of the newly-independent Ukraine instead.
In 1996, the peninsula adopted a new constitution, amending it to reflect its status as a highly autonomous region within Ukraine.
Moscow recognised Crimea as Ukrainian by signing the 1997 Friendship Treaty between Ukraine and Russia.
Tesla boss Elon Musk also said that Ukraine must "remain neutral," and in later tweets said, "victory for Ukraine is unlikely".