BIARRITZ, France (AP) — President Donald Trump is threatening to use the emergency authority granted by a powerful, but obscure federal law to make good on his tweeted "order" to U.S. businesses to cut ties in China amid a spiraling trade war between the two nations.

China's announcement Friday that it was raising tariffs on $75 billion in U.S. imports sent Trump into a rage and White House aides scrambling for a response.

Trump fired off on Twitter, declaring American companies "are hereby ordered to immediately start looking for an alternative to China." He later clarified that he was threat...