The U.S. State Department has approved the sale of $1.4 billion in arms to the island of Taiwan, a state official told the Associated Press on Thursday. The deal—which includes missiles, torpedoes, and technical support for early warning radar—is the first of its kind under the Trump administration. The last U.S. arms deal with Taiwan was approved in December 2015 for $1.8 billion. Like its predecessors, the sale prompted stark opposition from China, which considers Taiwan as part of its territory.

While Thursday’s deal threatens to exacerbate tension between the U.S. and China, U.S. officials insist they are operating in accordance with the Taiwan Relations Act, which requires the U.S. to sell weapons to Taiwan to ensure the nation’s self-defense. On Thursday, Heather Nauert, a state department spokeswoman, told the AP that the latest deal demonstrates the United States’s “support for Taiwan’s ability to maintain a sufficient self-defense policy.” She added that the U.S. has not deviated from the “one-China policy,” which prevents countries seeking diplomatic relations with China from maintaining the same ties with Taiwan.

Since 1979, the U.S. has described its dealings with Taiwan as “a robust unofficial relationship,” largely characterized by cultural and commercial ties. In December, China criticized a newly-elected President Trump for accepting a congratulatory phone call from Taiwan’s president, Tsai Ing-wen, marking the first time in decades that a U.S. president or president-elect had directly spoken to a Taiwanese leader. While the incident did little to damage U.S.-China relations, China urged the U.S. “to cautiously, properly handle [the] Taiwan issue to avoid unnecessary disturbance,” according to nation’s the state news agency.