David Cameron has said that the continued US failure to supply arms to Ukraine would undermine its own security, strengthen China and cast doubt on America’s reliability as an ally around the world. The UK foreign secretary, who attended the G20 meeting in Brazil earlier in the week, admitted that the effort to rally global support for the Ukrainian cause had been “damaged” by the fact that neither the US nor the UK had voted for a UN resolution calling for a ceasefire in Gaza. But he argued the damage had been mitigated by the UK’s clarification of its position. Cameron was speaking in New York on the second anniversary of Russia’s full-scale invasion of Ukraine at a time when the Republican speaker of the House of Representatives, Mike Johnson, is blocking a substantial package of military aid to Kyiv, leading to a severe ammunition shortage for Ukrainian troops. The foreign secretary was flanked by his German and Polish counterparts, Annalena Baerbock and Radek Sikorski, who made their own calls for US supplies to be resumed at a meeting organised in New York by the Wall Street Journal ahead of a UN security council meeting on Ukraine on Friday afternoon. Earlier in the day, Joe Biden had announced 500 new sanctions on Russia and a further 100 entities around the world for providing support to Russia, in an effort to squeeze Moscow’s revenues. But the foreign ministers made clear that arms supplies were the key in the struggle with Russia in Ukraine. Cameron sought to frame his argument in terms of competition with China, one of the few issues that unites Republicans and Democrats in the US Congress. “I know that lots of people in Congress are hugely concerned about the role of China and if you’re concerned about the role of China, you must make sure that Putin doesn’t win,” he said. He added that Beijing was enjoying “the fact that we’re, we’re not as united as we should be. I think that’s why the American package is so important.” In its relations with countries around the world, Cameron argued, China was saying “come have a relationship with us. America isn’t reliable.” The end of US military support to Ukraine, he added “would strengthen that argument they make in an enormous way”. Baerbock said the blockage of US aid “will be the biggest gift for Putin and will be the biggest gift for China”. “The Ukrainians are fighting like lions, but you cannot fight with bare hands,” Sikorski said. “They are running out of ammunition for anti-aircraft missiles that are protecting cities and when soldiers don’t have artillery shells, they have to do close combat fighting. That means that Ukrainian casualties are greater.” The European ministers face an uphill task persuading a Republican congressional leadership that is under the powerful sway of Donald Trump, an opponent of Ukrainian aid, and also resistant to allied pressure. Marjorie Taylor Greene, a far-right Republican congresswoman, responded to an earlier effort by Cameron to persuade Congress in Ukraine’s favour that the foreign secretary could “kiss my ass”. “I’m not trying to lecture or tell American congressmen what to do,” Cameron insisted on Friday. “I love my own country but I love America too. I think this is really important for America, for American security.” He admitted that the Israel-Hamas war in Gaza and western positions on the conflict had complicated efforts to build global solidarity against Russia. Earlier this week, the US vetoed a UN security council resolution calling for an immediate ceasefire for the third time, and the UK abstained. “The fact that we haven’t signed up for some of these resolutions and what have you, it does do some damage. There is no doubt about that,” Cameron said. “But I think when you explain how we really want to stop the fighting right now and have got a plan to do it, I think that helps to build some faith between the Arab world and what foreign ministers like myself and others say.” As European ministers sought to change minds in the Republican party, Volodymyr Zelenskiy held talks with a US congressional delegation in Lviv. The group – led by the Senate majority leader, Chuck Schumer – said it wanted to show that the US had not abandoned “the Ukrainian people”, or its Nato allies in Europe. Schumer said he and his fellow Democrats would “not stop fighting” until $61bn in military funding for Ukraine was delivered. House Republicans are currently blocking the assistance package, despite a 64-19 Senate vote in favour. “We believe we are at an inflection point in history and we must make it clear to our friends and allies around the globe that the US does not back away from our responsibilities,” Schumer said. The consequences of walking away would be “severe”, he warned, saying he would “make this clear” to the Republican speaker and to others obstructing aid back in Washington. Schumer told the Associated Press opposition to the national security package “may be the view of Donald Trump and some of the hard-right zealots. But it is not the view of the American people, and I don’t think it’s the view of the majority of people in the House or Senate.” Ukrainian commanders say with no new US weapons deliveries they are facing serious problems on the battlefield. They say that Ukrainian soldiers were forced to withdraw from the eastern city of Avdiivka last week because of an acute shortage of shells and ammunition. Further Russian gains were likely if no more aid arrived, they admitted. Ukraine is also running out of western-supplied interceptor missiles. A Russian drone strike killed three people early on Friday in the Black Sea port of Odesa, the regional governor, Oleh Kiper, said. Ukrainian air defences were only able to shoot down 23 out of 31 drones – a significantly lower number than in attacks last year. Earlier in Lviv Zelenskiy met with Denmark’s prime minister, Mette Frederiksen. The country has been one of Ukraine’s staunchest European allies. Frederiksen recently pledged to give all of Denmark’s artillery reserves to Ukraine and on Friday signed a long-term security agreement with Kyiv. It envisages giving €1.8bn ($1.9bn) in support. The two leaders visited Lviv’s Lychakiv cemetery and laid flowers at the grave of a Ukrainian soldier. Many hundreds of service personnel have been buried there since Russia’s full-scale invasion two years ago.