NEW YORK (Reuters) -BlackRock expects the artificial intelligence boom to continue to boost U.S. stocks next year and support economic growth more broadly, although rising U.S. government debt levels could threaten its upbeat 2025 forecasts. Innovations in AI technology will likely benefit U.S. stocks more than their European peers, while private markets will increasingly play a key role in financing AI-related infrastructure, the BlackRock Investment Institute, a research arm of the world's largest asset manager, said on Wednesday. "We stay risk-on ... and go further overweight U.S. stocks as the AI theme broadens out," it said in a 2025 outlook report based on views of senior portfolio managers and investment executives at BlackRock, which manages $11.5 trillion in assets.