The United States has pledged more weapons to help Ukraine prepare for a counterattack as Russian forces mount relentless attacks in the frontline city of Bakhmut. After weathering a punishing, months-long assault in eastern Ukraine, its military commanders have said a counter-offensive is not far off but have stressed the importance of holding towns, including Bakhmut, and inflicting losses in the meantime. "The question of our counter-attack is under active discussion by American and European political circles - perhaps to excess," said Serhiy Zgurets, director of the publication Defense Express. Ukrainian diplomats will have to convince allies a single advance pushing Russian troops back will not be sufficient for victory, he wrote on the Espreso TV website. "It will mean training our soldiers in NATO member-states, securing the equipment and ammunition we need, and planning to determine when and where to start the counterattack, or if it should be in several places at once." French President Emmanuel Macron was due in China on Wednesday after he and US President Joe Biden agreed to seek to engage Beijing to hasten the end of the war. China and Russia signed a "no limits" partnership accord early last year, just weeks before President Vladimir Putin sent tens of thousands of troops into Ukraine. China has refrained from criticising Putin's decision and has touted a peace plan for Ukraine. Zelenskiy headed to Poland, which has taken in more than a million Ukrainian refugees in the past 13 months. The NATO member has also played an important role in persuading other Western powers to supply battle tanks and other weaponry to Ukraine. The US on Tuesday unveiled $US2.6 billion ($A3.9 billion) more in military assistance for the government of President Volodymyr Zelenskiy, including three air surveillance radars, anti-tank rockets and fuel trucks. The US has now provided more than $US35 billion ($A52 billion) in military aid to Ukraine since Russia's invasion. "The main thing is not to lose time, not to lose the chance we have. Act now, help now," Zelenskiy told the US National Governors Association by video link. The Russian embassy in the US accused it of wanting to drag out the conflict as long as possible, Russian news agency TASS said. Tens of thousands of Ukrainian civilians and soldiers on both sides have been killed in what Russia calls a "special military operation" to rid the neighbouring nation of Nazis. The West calls the war an unprovoked assault to subdue an independent country. The battle for the eastern city of Bakhmut has been one of the bloodiest of the conflict, with heavy losses on both sides and the small city largely destroyed. The founder of Russia's Wagner mercenary force, Yevgeny Prigozhin, recently claimed his forces had captured the mining and logistics hub. Ukraine has repeatedly denied Russians control the city while acknowledging they have taken at least half of it. "In the Bakhmut sector, there was no letup in enemy actions aimed at storming the city of Bakhmut," the Ukrainian general staff said in a report on Facebook. "At least 20 enemy attacks were repelled here alone over the past 24 hours." Reuters could not verify the battlefield reports. Elsewhere, Russian media reported a Ukrainian drone crashed near the Zaporizhzhia nuclear power plant, as the chief of the global nuclear watchdog was expected in Russia for talks on the plant's security. International Atomic Energy Agency head Rafael Grossi was due to travel to Russia's Kaliningrad region on Wednesday, a week after visiting the Zaporizhzhia facility in southern Ukraine, which is controlled by Russian forces. Separately, the Kremlin said Belarussian President Alexander Lukashenko would travel to Moscow on Wednesday for two days of talks with Putin. Australian Associated Press