Amid ongoing trade tensions with Beijing, the US Navy sailed two warships within 12 miles of two Chinese-claimed islands in the South China Sea on Monday, the Navy’s 7th Fleet said. The two guided-missile destroyers USS Preble and USS Chung Hoon “sailed within 12 nautical miles of the Gaven and Johnson Reefs in order to challenge excessive maritime claims and preserve access to the waterways as governed by international law,” US Navy Cdr. Clay Doss, a 7th Fleet spokesman, told CNN. The US has long accused China of militarizing these islands, which are part of the Spratly Islands, most recently in a Pentagon report on China released last week. “In the South China Sea, China has continued militarization. Anti-ship cruise missiles and long-range surface-to-air missiles have been deployed to Spratly Islands outposts,” the report said, adding that the missiles deployed to the Spratly Islands in 2018 are the “most capable land-based weapons systems deployed by China in the disputed South China Sea.” While Doss said that Monday’s freedom of navigation operation was “not about any one country,” and not “about making political statements,” China has long protested these operations and has accused them of infringing on Beijing’s sovereignty. And although Chinese warships have challenged US vessels during previous such operations, the US Navy’s interactions with the Chinese military on Monday were described by officials as “routine” interactions that “were safe and professional.” The operation comes as US trade talks with China, once believed to be in their final stages, appeared to be put at risk after President Donald Trump placed the negotiations into question with a series of tweets threatening new tariffs on Monday.