The White House is urging US companies to beef up their cybersecurity efforts amid what it calls “evolving intelligence” indicating that Russia is considering the possibility of directing cyberattacks against the US.

       A statement on Monday from President Joe Biden warned that America was facing “a critical moment to accelerate our work to improve domestic cybersecurity and bolster our national resilience”.

       “I have previously warned about the potential that Russia could conduct malicious cyber activity against the United States, including as a response to the unprecedented economic costs we’ve imposed on Russia alongside our allies and partners. It’s part of Russia’s playbook. Today, my Administration is reiterating those warnings based on evolving intelligence that the Russian Government is exploring options for potential cyberattacks,” said the president.

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       His statement comes amid reports that Russia’s invasion of Ukraine has stalled on nearly all fronts and resulted in Moscow shifting its focus to the capture of the Black Sea port of Mariupol rather than topple Ukraine’s government.

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       Russia’s foreign ministry has, meanwhile, warned that the US and Russia may halt all diplomatic ties over the US’s continued vocal criticism of the invasion of Ukraine. Mr Biden’s characterisation of Vladimir Putin as a war criminal has been denounced by Russian officials as unforgivable.

       The US ambassador to Russia, John Sullivan, was summoned by Kremlin officials and given a note protesting Mr Biden’s recent statements on Monday, and according to the State Department used the meeting to demand consular access for US citizens detained in Russia.

       “Ambassador Sullivan took advantage of this encounter to demand that the Russian government follow international law, and basic human decency for that matter, and allow consular access to all U.S. citizen detainees in Russia, including those in pretrial detention,” said Ned Price, the State Department’s principal spokesman.

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       A Russian cyberattack on US companies could be seen as a major escalation of US-Russia tensions if the Biden administration definitively blames Mr Putin’s government for such a move; the White House has vowed to keep the US out of war in Europe over the invasion of Ukraine but anger between Moscow and Washington continues to boil in the wake of crushing western-led sanctions against Russia that have sought to isolate the country from the global economy.

       Ukrainian officials, meanwhile, continue to plead for more military and economic aid from Nato as well as the establishment of a no-fly-zone, which most experts agree would lead to a situation in which US forces would confront Russian aircraft, on the grounds of their belief that the war between Ukraine and Russia will soon inevitably spill out into the rest of Europe.

       Volodymyr Zelensky, Ukraine’s president, warned over the weekend that the world’s nations risk a “third World War” should his government’s peace talks with Moscow fail.