Ukraine will be “top of my agenda” this week at a meeting of leaders from the world’s most powerful economies, Keir Starmer has pledged, though he said he had “no plans” to follow the German chancellor, Olaf Scholz, and speak directly to Vladimir Putin. Starmer will meet world leaders on Monday at the G20 summit in Brazil, which the Russian president has declined to attend, sending his foreign minister, Sergei Lavrov, in his place. Speaking to reporters en route to the summit, the UK prime minister said it was significant that leaders were gathering almost 1,000 days into Russia’s war and said there had “got to be full support for as long as it takes”, citing the use of North Korean soldiers in the war as a particularly disturbing development. World leaders will gather in Rio de Janeiro for the summit, where there is significant division over the approach to Ukraine and an air of impotency given the imminent return of Donald Trump to the White House. The president-elect has signalled the US will take a different approach to funding Ukraine’s defence. Overnight, Russia fired more than 200 missile and drones across Ukraine, targeting the country’s energy grid, in the biggest attack on Ukraine since August and the first significant Russian assault since the US election. Starmer will attend the summit along with the Chinese president, Xi Jinping, the Indian prime minister, Narendra Modi, and the outgoing US president, Joe Biden. The UK prime minister said he had “no plans to speak to Putin”, when asked about Scholz’s call. He said: “We are coming up to the 1,000th day of this conflict on Tuesday: that’s 1,000 days of Russian aggression, 1,000 days of huge impact and sacrifice in relation to Ukrainian people, and recently we’ve seen the addition of North Korean troops working with the Russians, which does have serious implications. “I think on the one hand it shows the desperation of Russia but it’s got serious implications for European security, that added additional element, and for Indo-Pacific security – and that’s why I think we need to double-down on shoring up our support for Ukraine and that’s top of my agenda for the G20.” Starmer denied the G20 meeting was futile, with such extreme division between the leaders in attendance, not only on Ukraine but on economic issues, the climate and gender equality. The Argentinian president, Javier Milei, is a close ally of Trump and was the first world leader to visit the president-elect at his Florida residence. He is said to be mounting a number of obstacles to the formal communique. The French president, Emmanuel Macron, visited Milei en route to the summit in an attempt to ease tensions and salvage an agreement from the meeting.  “We’re meeting the biggest economies in the world in the next few days and my number-one mission is to grow our economy and to get inward investment into our country,” Starmer said. “So I’m going to use that opportunity at the G20 to do exactly that. And obviously, when it comes to security, there are really important issues right here, right now when it comes to Ukraine that I think are well worth it, and it’s important that we do pursue. And that’s why I’ll be trying to do what I can.”