The Trump administration has brought US onshore wind development to a halt citing national security concerns, representing a major escalation in the president’s crusade against renewable energy.

Approvals for about 165 onshore wind projects on private lands are being stalled by the Department of Defense, including wind farms that were awaiting final sign-off, others in the middle of negotiations, and some that typically would not require oversight by the department, according to the American Clean Power Association (ACP) and people close to the matter.

Wind farms require routine approval from the Defense Department to ensure they do not interfere with radar systems. This typically involves the level of risk being assessed and the developer paying an agreed sum for the army to update its radar filter system so it can locate the windmill. Some projects can be deemed not to pose a risk due to their distance from army facilities and flight paths. Normally these assessments can take as little as a few days to complete.