U.S. President Donald Trump on Tuesday said he planned to announce a 50% tariff on copper imports later in the day, surprising a global industry whose output is critical to electric vehicles, military hardware, semiconductors and a wide range of consumer goods.

Trump in February had ordered a probe into possible copper tariffs, with a November deadline, as part of efforts to rebuild U.S. production of the metal.

It was unclear whether the investigation - which was intended to evaluate imports of raw mined copper, copper concentrates, copper alloy, scrap copper and derivative products - has now concluded.

U.S. Commerce Secretary Howard Lutnick said on Tuesday the duties would likely be put in place by the end of July or August 1.

Here is what you need to know about U.S. copper imports:

US IMPORTS

The United States produces domestically just over half the refined copper it consumes each year. More than two-thirds of that is mined in Arizona, where the development of a massive new mine has been stalled for more than a decade. The remaining refined copper, just shy of 1 million metric tons annually, is imported.

While the White House framed the new tariffs as a way to counter China's dominance of the global market, the United States in fact imports most of its refined copper from the Americas.

Chile, Canada and Peru accounted for more than 90% of refined copper imports last year, according to the United States Geological Survey (USGS).

GLOBAL PRODUCTION

China dominates global copper refining, but most of the ore that feeds into its smelters is mined elsewhere, in particular in Latin America. Chile and Peru together mined roughly a third of global copper last year, according to the USGS.

However, China is expanding its control over world copper mining through its major investments in mines in the Democratic Republic of the Congo (DRC).

The DRC is now the world's second-largest copper miner after overtaking Peru, due in large part to massive Chinese investment in the African country's mining sector.

The Chinese copper smelting sector dwarfs all others. The country had dozens of copper smelters operating last year. Meanwhile, the United States has only two primary copper smelters, according to the USGS.