Ren Zhengfei, founder and chief executive officer of Huawei Technologies, left, speaks during an interview at the company's headquarters in Shenzhen, China, in January. Qilai Shen | Bloomberg | Getty Images

The brewing technology battle between the U.S. and China isn't just about 5G telecom equipment Chinese companies want to bring to the U.S. It's already starting to bleed into other tech categories, as shown in a new letter posted Monday from 11 senators and top officials from the departments of Energy and Homeland Security that called for a ban of Huawei-made solar technology. The letter sets the U.S. up to not only block smartphones and telecom equipment from Chinese companies such as Huawei, but nearly all tech it sees as a potential security threat.

The authors of the letter, including DHS Secretary Kirstjen Nielsen and Energy Secretary Rick Perry, say Huawei's "smart" solar grid products, which include control systems called "inverters" that are capable of connecting to the wider electrical grid, present a danger to "critical U.S. electrical systems and infrastructure." The energy-grid worries are a new strand in the increasingly tangled web of technology disputes between China and the U.S., and one that will only further complicate trade talks. In just the past few months, the two countries have sparred over technology theft, knowledge-transfer laws in China, purported violations of U.S. sanctions against Iran, trade-secrets theft of tech from companies such as T-Mobile, allegations of Chinese spying using exported equipment in U.S. networks and more.

The letter shows that U.S. officials will continue to fight against a full range of China-manufactured equipment, not just network equipment that would enable 5G connectivity. The issue will likely heighten the debate between U.S. officials, who say China's tech companies work hand-in-hand with the Chinese government to create tech equipment that can be used offensively against the U.S., and Chinese officials and business leaders, who have said these accusations are mere protectionism by the U.S. Huawei's inverters are used by residential, commercial and public utility customers. Huawei offers a full range of solar panel products in addition to the control systems, including the control systems and software to run and monitor power plants that process solar energy. Huawei's equipment has been adopted on a large scale by installations across Europe and, most recently, in Saudi Arabia.