The U.K. has cut coal out of its diet in a desperate bid to decarbonize. It's a noble step in the fight to reduce carbon emissions and slow global warming, but the path to clean energy has many obstacles, and not all are technological. Solar and wind energy can only partly and intermittently supply the energy left by the shift away from coal, which has forced the British government to turn to natural gas to fill the vacuum. But what about the low-carbon, fossil fuel-free alternative that is nuclear energy? There, geo-political tensions stand in the way of clean power generation.

Reflecting the increasingly sour relationship between the London and Beijing, the U.K. government is hoping to nudge China General Nuclear (CGN) out of its 20% ownership of the £20 billion Sizewell nuclear power station in Suffolk and open the project up to new (and preferably North American) investors, the Financial Times reported Monday. It is the U.K.'s latest step to remove CGN from all future nuclear energy projects in the U.K. and protect its critical infrastructure from China.

The change in British mood affects other nuclear projects as well, including as the Bradwell-on-Sea plant in Essex which was to be owned by CGN, as well as the heavily delayed Hinkley Point C project—raising questions about the future of the U.K’s energy make-up.

Tensions with CGN originally began in 2019, when the U.S. put the Chinese company on an export blacklist, accusing them of stealing U.S. technology for military purposes. At the time, Trump warned the U.K. against Chinese involvement in nuclear power and since then U.S. allies in Europe and Asia have been looking to avoid reliance on Chinese technology.

The move is the next step in repossessing ownership of energy and infrastructure assets deemed “critical” to the U.K., similar to a 2020 decision to force Chinese telecoms company Huawei out of Britain’s 5G network. However, kicking out China out of nuclear projects in the U.K. may push Britain's net zero plans further out; it remains to be seen if the U.K. can build nuclear plants on its own.

Nuclear tensions

China has been collaborating with the U.K. on its nuclear power since a 2015 agreement between Britain's then-Prime Minster David Cameron and China. The deal put CGN as a 20% partner in the development of the planned Sizewell C plant in the Suffolk coast, with an option to participate in its construction.

The leader of the Sizewell project is EDF, the French state-backed utility, which is building out the power plants using new European Pressurized Reactor (EPR) technology. According to reports, discussions have already begun taking place between the U.K. government and EDF to find new partners for the project, preferably attracting a North American infrastructure investor to the project.

There are three nuclear plants being built with EPR technology—Finland's Olkiluoto plant, France's Flamanville and the U.K.'s Hinkley Point C—and they have all gone through embarrassing delays and cost overruns during construction. The only operating nuclear plant that uses EPR technology—China's Taishan—was built by CGN.

At the moment the Chinese appear to be the only ones who know how to build an operating EPR plant, as EDF have been unable to bring their three projects across the finish line. Additionally, if the move to exclude China goes through, plans for the Bradwell-on-Sea plant—a project that would be entirely financed and built by CGN, which intends to install its own Hualong HPR1000 reactor technology—is also likely to collapse, as the U.K. intends to reject any Chinese participation in nuclear plant construction.

Industry sources express skepticism that the U.K. government and France's EDF can build the remaining EPR reactors without the aid of China's CGN. "The French will say 'we don't need the Chinese to build the reactors,'" a senior nuclear industry advisor told Fortune, "but they absolutely do."