LONDON - Britain and the United States agreed on a multi-billion-dollar tech deal during US President Donald Trump's state visit to boost fast-growing fields such as AI, quantum computing and nuclear, the British government said Tuesday.

The Tech Prosperity Deal aims to accelerate AI research for new drugs, faster treatments, and better cancer care, while also supporting civil nuclear projects, said the official statement.

As part of the deal, Microsoft will invest $30 billion in AI infrastructure in Britain, while Google will open a data center in Waltham Cross, Hertfordshire, as part of a two-year multi-billion-dollar investment in Britain.

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However, critics have warned against Britain's growing dependence on the United States and American technology with potential consequences.

US news outlet Politico quoted Gaia Marcus of the Ada Lovelace independent research institute as warning that "We mustn't just focus on today's figures if the cost is technological lock-in tomorrow, limiting our ability to seek alternatives in the future."

Chi Onwurah, chair of the House of Commons Science, Innovation and Technology Committee, cautioned, "true technology sovereignty cannot mean being dependent on one investor or country".

Trump arrived in London on Tuesday evening for his second state visit to Britain. Nearly 100 protesters gathered along the streets outside Windsor Castle that night, chanting slogans against the visit and waving placards reading "Stop Hate, Stop Trump" and "Hate Never Made Any Nation Great."

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On Wednesday afternoon, thousands of demonstrators marched through central London to protest against the US President's second state visit to Britain, as Trump was being feted at Windsor Castle by the royal family.

Protesters waved placards criticizing US policies on immigration, Gaza and climate change, marching to the sound of trumpets and drums from Portland Place to Parliament Square.

US citizen Amanda said that she traveled to London from Los Angeles just for the protest. "I think everything is just very messed up right now. We don't have good leadership and I'm very worried for the direction that the United States is taking and the world," she said.

Philip Threlfall, a resident from Hitchin, a town in Hertfordshire, told Xinhua that building such a center is "inevitable," but "they are gonna be a bad thing for everybody, just gonna eat power, eat up wetland and produce the same old rubbish multi-times over".

Metropolitan Police said Wednesday that they estimated up to 5,000 people were in attendance. They also announced Tuesday that more than 1,600 officers would be deployed for the large demonstration and warned the event must conclude by 7 pm local time.

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The demonstration was organized by the "Stop Trump Coalition" group.

According to Buckingham Palace, Trump and British Prime Minister Keir Starmer are scheduled to hold a bilateral meeting on Thursday, the last day of his visit, at Chequers, the prime minister's country residence.