By Stephen NellisSAN FRANCISCO, July 24 (Reuters) - Nvidia, Microsoft and other tech heavyweights made a public case to lawmakers on Friday in favor of open-source ‌AI models, wading into a debate roiling the business and policy worlds over ‌who controls the powerful technology. The letter adds to the growing debate about open-source models that are harder to regulate, such as Nvidia's own and those released ‌in recent weeks by Chinese ⁠labs, and the closed-source models controlled by specific companies such as OpenAI and Anthropic. The CEOs of Microsoft and defense contractor Palantir Technologies have publicly argued that open-source models their customers can run inside their own data centers will help control ​AI ​costs. Tech leaders have also chafed at controls that ​OpenAI and Anthropic build into their ‌models. Hugging Face, the AI coding collaboration site that was hacked by a rogue OpenAI model, this week said that it had to use a Chinese open-source model to defend against the attack because closed-source models have restrictions on use for cybersecurity work.