President Joe Biden welcomed Prime Minister Rishi Sunak for wide-ranging talks on Thursday as the British leader made his first White House visit as premier.The leaders' Oval Office talks are expected to cover the war in Ukraine, China, economic security, international cooperation on regulating the growing field of artificial intelligence, and more. Biden and Sunak have already had four face-to-face meetings since Sunak became prime minister in October, but the talks in Washington will offer the two leaders a chance for their most sustained interaction to date.White House press secretary Karine Jean-Pierre said the 15-month-old Russian invasion of Ukraine will be "top of mind." The U.S. and U.K. are the two biggest donors to the Ukraine war effort and play a central role in a long-term effort announced last month to train, and eventually equip, Ukrainian pilots on F-16 fighter jets.Sunak also is looking to make the case to Biden for U.K. Defense Minister Ben Wallace to succeed outgoing NATO Secretary-General Jens Stoltenberg, who is set to end his term leading the 31-member alliance in September. Stoltenberg is slated to meet with Biden in Washington on Monday, and leaders from the alliance are set to gather in Lithuania on July 11-12 for their annual summit."The two leaders will review a range of global issues including our economic partnership or shared support of Ukraine as it defends itself against Russia’s war of aggression, as well as further action to accelerate the clean energy transition," Jean-Pierre said. "The president and the prime minister will also discuss the joint U.S.-U.K. leadership on critical emerging technologies as well as our work to strengthen our economic security."Sunak is keen to make the U.K. a key player in artificial intelligence and announced that his government will gather politicians, scientists and tech executives for a summit on AI safety in the fall.He said it was vital to ensure that "paradigm-shifting new technologies" are harnessed for the good of humanity."No one country can do this alone," Sunak said. "This is going to take a global effort."Sunak's visit comes as U.S. and British intelligence officials are still trying to sort out blame for the breaching of a major dam in southern Ukraine, which sent floodwaters gushing through towns and over farmland. Neither Washington nor London has officially accused Russia of blowing up the Kakhovka hydroelectric dam.Sunak said Wednesday that U.K. intelligence services are still assessing the evidence, but "if it does prove to be intentional, it will represent a new low ... an appalling barbarism on Russia’s part.""Russia throughout this war has used as a deliberate active strategy to target civilian infrastructure," he told broadcaster ITV in Washington.The two sides are hoping to demonstrate that the U.S.-U.K. relationship remains as strong as ever despite recent political and economic upheaval in the U.K. Sunak is one of three British prime ministers Biden has dealt with since taking office in 2021, and the administrations have had differences over Brexit and its impact on Northern Ireland.There also have been some awkward moments between the two leaders in the early going.Biden, at a White House celebration in October to mark the Hindu holiday of Diwali, noted the elevation of Sunak, who is the U.K.'s first leader of color and the first Hindu to serve in the role, as a "groundbreaking milestone" but he badly mangled the pronunciation of Sunak's name.At a March meeting in San Diego with Sunak and Australian Prime Minister Anthony Albanese to announce plans to sell Australia nuclear-powered attack submarines, Biden jokingly told Sunak "Maybe you can invite me to your home in California." The lighthearted aside resurrected old political baggage for Sunak, whose political aspirations briefly dimmed as he faced an ethics investigation last year after it emerged that he had possessed a U.S. green card two years after being appointed chancellor of the exchequer. Sunak, a former hedge fund manager with an MBA from Stanford University, and his wife own a home in California.Nonetheless, there's a sense in the Biden administration that the U.S.-U.K. relationship is back on more stable footing after the sometimes choppy tenure of Boris Johnson and the 45-day premiership of Liz Truss."I think there’s a sense of relief to some degree, not just in the White House, but throughout Washington, that the Sunak government has been very pragmatic and maintained the U.K.’s robust commitment to Ukraine and to increasing defense spending,” said Max Bergmann, director of the Europe, Russia and Eurasia program at the Center for Strategic and International Studies. He added that with Sunak, there’s also been “somewhat of a return to pragmatism" on economic issues and relations with the European Union post-Brexit.Sunak opened his two-day Washington visit on Wednesday by laying a wreath at the Tomb of the Unknown Soldier at Arlington National Cemetery. He met with key congressional leaders, including Republican House Speaker Kevin McCarthy, as well as business leaders. He also attended a Washington Nationals baseball game.Shortly before departing for Washington, Sunak announced that several U.S. companies were making $17 billion (£14 billion) in new economic investments in the U.K.The chairs of the Congressional-Executive Commission on China, Republican Rep. Chris Smith and Democratic Sen. Jeff Merkley, on Wednesday, wrote to Sunak asking him to work with the Biden administration on Hong Kong policy and push for the release of jailed media tycoon Jimmy Lai and other activists.Lai's son, Sebastien Lai, last month in testimony before the U.S. committee expressed disappointment that the U.K. had not condemned his father’s detention publicly and had not taken a stronger stance in advocating for his release. The elder Lai founded the now-shut pro-democracy newspaper Apple Daily and faces charges under Hong Kong’s security law and colonial-era sedition law."A robust stance by the U.K. government is critically important, given your oversight of the Sino-British Declaration and the millions of Hong Kongers who hold British citizenship or British National (Overseas) passports," the lawmakers wrote. "The erosion of Hong Kong’s promised autonomy and the dismantling of a free press and the rule of law are issues of global concern."___Associated Press Diplomatic Writer Matthew Lee contributed to this report.