Rishi Sunak has said if Russia was responsible for the destruction of a dam in Ukraine, it would be a “new low” for Moscow in the invasion. Speaking to reporters on board his official plane to Washington, where he is to hold pre-planned talks with the US president, Joe Biden, Sunak said the UK cannot yet know for certain who was to blame for the collapse of a vast dam on the Dnipro River that Kyiv said was blown up by Russian forces to hamper a Ukrainian military push. “Our military and intelligence agencies are currently looking at it so it’s too soon to preempt that and make a definitive judgment,” he said. “But what I can say is, if it is intentional it would represent the largest attack on civilian infrastructure in Ukraine since the start of the war, and would demonstrate the new lows that we would have seen from Russian aggression.” Sunak added: “I’ll be discussing Ukraine with President Biden more generally. But the immediate response is humanitarian. We had already put resources and funding in place to support both the UN and the Red Cross to respond to situations like this. “They are now able to divert those resources to particularly help the humanitarian response and the evacuation in this area.” Sunak was heading to Washington DC for a meeting with Biden that Downing Street hoped will be marked by warm words over trade ties, but now risks being overshadowed by the rapidly unfolding situation in Ukraine. In a swift, two-day visit, the prime minister will be granted the full force of US diplomacy, including a joint press conference with Biden and a stay in Blair House, the official presidential guest residency, whose last occupant from No 10 was David Cameron. Sunak will enjoy the attention paid, not least as a sign of the White House treating him as a more reliable and relatable UK counterpart after the turbulence of Boris Johnson and then Liz Truss. The prime minister faces a packed schedule, including his White House bilateral meeting with the president, an event alongside a mass of US business leaders, and a baseball game – although the original plan for Sunak to make the first pitch at the Washington Nationals’ stadium has been discarded by No 10 given the potential for high-profile mishap. It is, nonetheless, a trip without any immediate policy purpose, with even mooted focuses such as Sunak pushing for the UK to host a global regulator on AI, or to make the case for Ben Wallace as the next Nato secretary general, not necessarily featuring in discussions. Broader issues of economic security would be a key focus, Sunak’s official spokesperson said before the trip, comprising “everything from protecting our supply chains and insulating our economies from manipulation from hostile states, to increasing our mutual investment in green technology to governing the development and use of artificial intelligence”. While Ukraine was already very much on the agenda, along with wider defence cooperation, the leaders will meet amid a dangerous and unstable situation in southern Ukraine. Many thousands of people are being moved from the waters unleashed by the already overfilled dam, while it is feared the ecological consequences will be huge and long-lasting. Sunak and Biden were already scheduled to discuss “how we can sustain the huge level of global support for Ukraine, while providing them with the capabilities they need, including air defence”, the prime minister’s spokesperson said. With a formal post-Brexit free-trade deal with the US now not on the horizon, Sunak will instead push for other ways to boost economic links, including at a gathering of US business leaders hosted by Mary Barra, the chief executive of General Motors. Sunak will spend a period on Wednesday meeting individual senators and Congress members on Capitol Hill, although No 10 has yet to say who has been lined up. He will also lay a wreath at Arlington National Cemetery. Labour has urged Sunak to make progress in getting some sort of agreement on UK market access after Biden’s landmark Inflation Reduction Act, which directs many billions of dollars in subsidies and tax credits toward renewable energy and other green measures, a plan the UK government has labelled “protectionist”. While Downing Street will relish the footage of Sunak in the Oval Office, and alongside Biden at the White House press conference lecterns, it has dodged the proposed idea of Sunak hurling the first pitch when the Nationals take on the Arizona Diamondbacks on Wednesday evening, a game officially designated as a US-UK friendship event. When asked about the proposition on this transatlantic flight, the prime minister brushed off the rejection, saying: “My sport is more cricket than baseball in any case.” Sunak then offered his opinion on the question bothering English cricket lovers: who will replace injured spin bowler Jack Leach for the opening Ashes test match against Australia. “Either the SOS for Moeen Ali, or indeed that 18-year-old who played that one Test [against Pakistan in December], [Rehan] Ahmed,” said Sunak, adding he was “very confident” about England’s prospects.