Joe Biden says US will defend 'every inch of NATO' - as Moscow welcomes China's help in 'resolving' Ukraine war
Joe Biden has said the US will defend "literally every inch of NATO" in the face of Russian aggression - as Moscow welcomed China having a more active role in "resolving" the Ukraine war.
The US president has met leaders from the Bucharest Nine - a collection of nations in the most eastern parts of the NATO alliance that came together in response to Putin's 2014 annexation of Crimea from Ukraine.
The alliance includes Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia.
The countries have expressed concerns that Mr Putin could launch military action against them next if he is successful in Ukraine.
Biden's place in history clearer but worrying times loom
President says Ukraine's allies have 'iron will'
"You're the frontlines of our collective defence," Mr Biden said of the group.
"And you know, better than anyone, what's at stake in this conflict. Not just for Ukraine, but for the freedom of democracies throughout Europe and around the world."
He pledged that NATO's mutual-defence pact is "sacred" and that "we will defend literally every inch of NATO".
China's top diplomat meets Putin in Russia
Meanwhile, Russia has welcomed Beijing taking a more active role in efforts to "resolve" the war after China's top diplomat Wang Yi met Vladimir Putin in Russia.
Following the meeting, Mr Putin said he was looking forward to a visit to Moscow by Chinese President Xi Jinping.
No other countries could influence the relationship between China and Russia, he added.
Russia's foreign ministry spokeswoman Maria Zakharova said Mr Wang's trip had shown Moscow and Beijing agreed on many issues.
Ms Zakharova praised China's "balanced approach" towards the war.
"We welcome China's readiness to play a positive role in resolving the Ukrainian crisis," Ms Zakharova said.
Mr Wang was quoted in Russian state media as saying China will "firmly adhere to an objective and impartial position and play a constructive role in the political settlement of the crisis".
China has refused to criticise the invasion of Ukraine while condemning sanctions imposed on Russia.
In return, Russia has supported China amid tensions with the US over Taiwan.
Russia is due to begin military exercises with China in South Africa on Friday and has sent a frigate equipped with new generation hypersonic cruise missiles.
A Russian officer said Moscow would fire artillery, but not the missiles, whose speed makes them difficult to shoot down.
Click to subscribe to the Sky News Daily wherever you get your podcasts
Putin 'proud' of those fighting in Ukraine
The top Chinese diplomat's visit to Russia came as Mr Putin spoke at a huge rally in Moscow.
He said Russia is "proud of those who are fighting in Ukraine to defend the fatherland", adding that the "whole country" supports them.
Chants of "Russia, Russia, Russia" were heard around him as he spoke.
Some 200,000 people had gathered in Moscow to hear Mr Putin's address.
Biden criticises Russia's move to pause nuclear treaty cooperation
Meanwhile, Mr Biden said Mr Putin had made a "big mistake" in deciding to suspend participation in the last nuclear treaty between the US and Russia.
He made the comment to reporters as he arrived at the presidential palace in Warsaw for a summit of the Bucharest Nine countries.
Moscow has insisted its decision to pull out of the New START treaty does not raise the risk of nuclear war.
The move is expected to have an immediate impact on US visibility into Russian nuclear activities as it allowed each side to conduct up to 18 inspections of strategic nuclear weapons sites each year.
The treaty also imposes a cap on the number of strategic nuclear warheads that the US and Russia can deploy.
Russia has said it is not withdrawing from the pact altogether and would respect the caps on nuclear weapons set under the treaty.
One of the fiercest battles of the war is intensifying
Russian mercenary boss releases image of dead soldiers
"I do not believe that the decision to suspend the New START Treaty brings us closer to nuclear war," deputy foreign minister Sergei Ryabkov said, according to the Interfax news agency.
Despite the foreign minister's comments, Russia's former president Dmitry Medvedev said the world was "on the verge of a global conflict".
"If the US wants Russia's defeat, we have the right to defend ourselves with any weapons, including nuclear," he wrote.
Speaking of Russia decision to pause its cooperation in the New START treaty, Mr Biden said: "It's a big mistake."
The remark, and his promise that the US would protect eastern NATO territory, came a day after he gave a highly-anticipated speech in the gardens of the Royal Castle in Warsaw.
Mr Biden warned that Russian aggression, if unchecked, wouldn't stop at Ukraine's borders. "Appetites of the autocrat cannot be appeased," he said. "They must be opposed."
He also met Moldovan President Maia Sandu in Warsaw, who last week claimed Moscow was behind a plot to overthrow her country's government using external saboteurs.
She spoke out after Ukrainian President Volodymyr Zelenskyy said his country had intercepted plans by Russian secret services to destroy Moldova. Those claims were later confirmed by Moldovan intelligence officials.
Meanwhile, Hungarian Prime Minister Viktor Orban, the right-wing populist leader who argued last week that the European Union is partly to blame for prolonging Russia's war in Ukraine, skipped the Bucharest Nine meeting with Mr Biden.
President Katalin Novak attended instead.
'We must break the cycle of Russian aggression'
NATO Secretary General Jens Stoltenberg, who attended the meeting, said: "We don't know when the war will end, but when it does, we need to ensure that history does not repeat itself."
Pointing to past Russian actions in Georgia and Ukraine, he said: "We cannot allow Russia to continue to chip away at European security. We must break the cycle of Russian aggression."
Meanwhile, Kyiv has said there can be no talk of peace with Russian troops in Ukraine.