Rishi Sunak’s arrival in No 10 as Britain’s third prime minister in less than two months drew calls for stability from Europe and continued support from Ukraine, as well as cheers in New Delhi and praise as a “groundbreaking milestone” from the US. In Kyiv, Volodymyr Zelenskiy wished the UK’s new head of government success in overcoming “all the challenges facing British society and the whole world today”. The Ukrainian president added: “I’m ready to continue strengthening the strategic partnership together!” Britain has been one of Ukraine’s most vocal backers since Russia invaded its eastern neighbour in February and Moscow has repeatedly said in recent weeks that its relations with London were unlikely to improve no matter who occupies No 10. The Kremlin reaffirmed that position on Tuesday. “At the moment we see no grounds for hope that there will be any positive changes in the foreseeable future,” said its spokesperson, Dmitry Peskov. Elsewhere, world leaders lauded the significance of Sunak’s victory as the UK’s first prime minister of colour and the youngest in modern political history. In the US, Joe Biden tweeted his congratulations, saying he looked forward to “enhancing our cooperation on issues critical to global security and prosperity, including continuing our strong support for Ukraine”. In impromptu comments at a Diwali celebration in the White House on Monday night, the US president had described Sunak’s nomination as “pretty astounding, a groundbreaking milestone and it matters” – although he rather spoiled the effect by appearing to pronounce Sunak’s name as Rashid or Rashi Sanook. News that a Hindu son of Indian immigrants had won the leadership race also raised cheers in India, where some found pride in the fact that a person of Indian heritage would be running a country it was once colonised by. A strap across the bottom of the screen on New Delhi Television ran the words: “Indian son rises over the empire,” while a Times of India headline said: “UK rings in Rishi raj on Diwali.” India’s prime minister, Narendra Modi, sent his “warmest congratulations” to Sunak, saying he looked forward to “working closely together on global issues” and adding: “Special Diwali wishes to the ‘living bridge’ of UK Indians, as we transform our historic ties into a modern partnership.” European leaders, who have watched the political crisis engulfing post-Brexit Britain with growing consternation, couched their well-wishes with statements on the need for a stable and predictable neighbour. “Congratulations to Rishi Sunak, who has become prime minister of the United Kingdom,” the French president, Emmanuel Macron, tweeted. “Together we will continue working to tackle the challenges of the moment, including the war in Ukraine and its many consequences for Europe and the world.” The European Council president, Charles Michel, tweeted his congratulations on Monday night, emphasising that Brussels and London faced shared challenges. “Working together is the only way to face common challenges … and bringing stability is key to overcoming them,” he wrote. The president of the European parliament, Roberta Metsola, said the EU legislature was committed to having “a strong and constructive relationship” with the UK. “At a time of enormous challenges, Europe needs political and economic stability. Our core interests remain the same,” she said. The Dutch prime minister, Mark Rutte, tweeted his “sincere congratulations” to Sunak, adding: “I look forward to working with him to further deepen the longstanding, excellent ties between [the Netherlands and the UK] and to working shoulder to shoulder in Nato.” Rutte said last week that Truss’s successor would be his “number five” British leader, and Luxembourg’s prime minister, Xavier Bettel, in power since 2013, quipped: “I hope I can recall how many British PMs I’ve survived.” Closer to home, the Irish taoiseach, Micheál Martin, said he looked forward to working with Sunak “on the important issues we face on these islands and globally”. Australian and New Zealand leaders were quick to send congratulations. Australia’s treasurer, Jim Chalmers, called Sunak a great friend of Australia and lauded the significance of Britain being about to have its first prime minister of Asian descent. “I don’t think it’s insignificant a country like the United Kingdom has its first prime minister of colour,” he said on Tuesday. Sunak is a “good friend of New Zealand”, said its acting prime minister, Grant Robertson, adding he hoped the Tory leader would help seal a free trade agreement with his country. “Clearly the UK is facing some very significant economic issues at the moment, he’s said that himself. Inflation up over 10%, the energy crisis, the war in Ukraine, so it’s going to be a very tough time for him,” he said.