AI-led U.S. bull market nears four years as risks build

The U.S. stock market has risen sharply for almost four years, with AI investment helping companies earn more.

The S&P 500 is near record highs, and its gains have been especially strong in technology and AI-related companies.

But investors are watching for signs that AI spending may not deliver the profits companies expect.

Higher interest rates and rising government bond yields could also weigh on stocks.