China’s growing foothold over the Panama Canal isn’t just fueling its own commercial interests, it also appears to be helping America’s adversaries engage side-step sanctions, court documents obtained by the Daily Caller News Foundation show.

China has expanded its presence considerably in the Panama Canal since former President Jimmy Carter sold the shipping lane to Panama for $1 in 1977, and is funding multi-billion dollar infrastructure projects in the surrounding countryside while buying up ports to solidify its foothold. It’s also been a boon to American adversaries, like Iran.

Panamanian court documents obtained by the DCNF show how Iran appeared to have used proxy firms based in Hong Kong, China, to register ships in the Panama Canal and attempted to reap the benefits of chartering its ships.

“Given the presence of Chinese companies in port operations and infrastructure near the canal, U.S. officials worry that Beijing may seek commercial or strategic leverage in the region,” Dr. Umud Shokri, senior visiting fellow at George Mason University with expertise in foreign policy, told the DCNF. “The Trump administration’s efforts to regain influence over the canal reflect Washington’s broader view of the waterway as a critical national security asset.”