Stiffer competition for the tech giants at the forefront of the artificial intelligence boom prompted investors to reassess the companies’ sky-high valuations.

Meta, Apple, Microsoft and Tesla report quarterly results, as analysts start to focus more on AI results. Earnings are also due from Starbucks and Boeing.

European tech shares came under pressure on Monday, after Chinese tech startup DeepSeek's low-cost artificial intelligence model sparked worries about returns in the AI business and the need for costly chips.

Chinese startup DeepSeek's cheaper AI is sharpening investor scrutiny of the billions U.S. tech giants are pouring to develop the technology and analysts say it will dominate this week's much-awaited results from industry bellwethers.

Nvidia shares closed down almost 17%, posting its biggest drop since March 2020 and erasing nearly $600 billion from the company's market cap. Broadcom fell 17.4%, and other chip stocks like Micron declined 11.

The tech-heavy Nasdaq index lost nearly 2.7 percent in early trading, with chipmaker Nvidia down nearly 12 percent.