Two U.S. warships sailed through waters claimed by China in the South China Sea, an action that could infuriate Beijing as a new round of trade talks gets underway ahead of a looming deadline.

The guided-missile destroyers traveled within 12 nautical miles of Mischief Reef in the disputed Spratly Islands, Reuters reported, citing an unidentified U.S. official. The reef is one of seven artificial structures that China has built by reclaiming land, and which the U.S. alleges the Chinese have militarized.

The sail-by comes as U.S. Trade Representative Robert Lighthizer leads a group of administration officials to Beijing, the latest high-profile effort to resolve the two countries’ trade dispute before March 1—when the Trump administration says it will more than double tariffs on $200 billion of Chinese goods if a deal hasn’t been reached.

China claims as territory more than 80 percent of the South China Sea. Five other countries, including Vietnam and the Philippines, have competing claims. The U.S. regularly sends vessels through the waters to assert its right to sail in what it considers international waters.

China urged the U.S. to halt “provocative actions” after a U.S. guided-missile destroyer conducted a so-called freedom-of-navigation patrol near the disputed Paracel Islands in the waters in early January. The U.S. often doesn’t officially announce sail-bys in the South China Sea.

U.S. Indo-Pacific Command didn’t immediately respond to an email seeking confirmation for the transit reported by Reuters.