Russian troops and mercenaries were closing off the last access routes to the besieged Ukrainian city of Bakhmut on Friday, on the cusp of Moscow's first major victory in half a year after the bloodiest fighting of the war. The head of Russia's Wagner private army said the city, which has been blasted to ruins, was now almost completely surrounded, with only one route out left open for Ukraine's troops. Reuters journalists west of the city saw Ukrainians digging new trenches for defensive positions there, while the commander of a Ukrainian drone unit inside the city for months said he had been ordered to withdraw. Victory in Bakhmut, with a pre-war population of about 70,000, would give Russia the first major prize of a costly winter offensive after it called up hundreds of thousands of reservists last year. It says it would be a stepping stone to capturing the surrounding Donbas region, a major war aim. Ukraine, which recaptured swathes of territory in the second half of 2022 but whose forces have been on the defensive for three months, says the city has little strategic value but that the huge losses there could determine the course of the war. In a video filmed on a rooftop in an undisclosed location, Wagner boss Yevgeny Prigozhin, dressed in a combat uniform, said he was calling on President Volodymyr Zelenskiy to order the evacuation of Bakhmut to save the lives of Ukrainian soldiers. "Units of the private military company Wagner have practically surrounded Bakhmut. Only one route (out) is left," he said. "The pincers are closing." The camera then panned to show three captured Ukrainians - an older man and two young boys - who looked frightened and asked to be allowed to go home, in what appeared to be a choreographed appearance under extreme stress. Both sides say they have inflicted devastating losses in Bakhmut. Kyiv has insisted its forces are still holding out there, while acknowledging that the situation has deteriorated this week. Volodymyr Nazarenko, a deputy commander in the National Guard of Ukraine, told Ukrainian NV Radio the situation was "critical", with fighting going on "round the clock". "They take no account of their losses in trying to take the city by assault. The task of our forces in Bakhmut is to inflict as many losses on the enemy as possible. Every meter of Ukrainian land costs hundreds of lives to the enemy," he said. "We need as much ammunition as possible. There are many more Russians here than we have ammunition to destroy them." The commander of a Ukrainian drone unit active in Bakhmut, Robert Brovdi who goes by the name "Madyar", said in a video posted on social media that his unit had been ordered by the military to withdraw immediately from the city. He said he had been fighting there for 110 days, and gave no reason for the order to leave. Scholz in Washington German Chancellor Olaf Scholz was due to meet US President Joe Biden at the White House to discuss additional military aid to Ukraine. Germany makes the Leopard tanks that are expected to be the core of a new Ukrainian armored force when they arrive later this year. Scholz has been criticized by some Western allies for taking a cautious public stance towards arming Ukraine, although he has overseen a dramatic shift in policy from a country that was Russia's biggest energy customer on the eve of the war. Washington will announce its latest military aid package worth $400 million, mainly comprising ammunition and armored vehicles. The United States has provided nearly $32 billion in weaponry to Ukraine since the invasion. Biden and Scholz could also touch on concerns that China may provide lethal aid to Russia, a senior administration official said. The Biden administration is sounding out close allies about the possibility of imposing new sanctions on China if Beijing provides military support to Russia, US officials and other sources said. China has denied considering such assistance, and US officials have not publicly provided evidence for their suspicions. Asked by reporters whether potential sanctions against China would be a topic for Biden and Scholz, White House national security spokesman John Kirby said "the issue of a third party support to Russia could come up." Tens of thousands of Ukrainian civilians and soldiers on both sides are believed to have been killed since Russia invaded its pro-Western neighbor a year ago. Moscow, which claims to have annexed nearly a fifth of Ukraine, says Kyiv posed a security threat. Ukraine and its allies say the invasion was an unprovoked war to conquer land. On the sidelines of a G20 foreign ministers meeting in India, US Secretary of State Antony Blinken briefly met Russian Foreign Minister Sergei Lavrov face to face for the first time since the invasion. Blinken told Lavrov to end the war, and urged Moscow to reverse its suspension - announced last week - of the last remaining nuclear arms control agreement, US officials said. Speaking at a forum in the Indian capital on Friday, Blinken said Russia cannot be allowed to wage war with impunity, otherwise it would send "a message to would-be aggressors everywhere that they may be able to get away with it too."