Trade barriers

FILE - In this Sept. 22, 2005 file photo a steel worker takes a sample at the blast furnace of ThyssenKrupp steel company in Duisburg, western Germany. Ordering combative action on foreign trade, President Donald Trump has declared that the U.S. will impose steep tariffs on steel and aluminum imports, escalating tensions with China and other trading partners and raising the prospect of higher prices for American consumers and companies. (AP Photo/Frank Austin, file)

President Donald Trump listens during a meeting with steel and aluminum executives in the Cabinet Room of the White House, Thursday, March 1, 2018, in Washington. Trump's announcement that he will impose stiff tariffs on imported steel and aluminum has upended political alliances on Capitol Hill. (AP Photo/Evan Vucci)

A light turned red in front of the Krupp Mannesmann steel factory in Duisburg, Germany, Friday, March 2, 2018. U.S. President Donald Trump risks sparking a trade war with his closest allies if he goes ahead with plans to impose steep tariffs on steel and aluminum imports, German officials and industry groups warned Friday. (AP Photo/Martin Meissner)

In this Jan. 25, 2018 photo, Sen. Lindsey Graham, R-S.C., speaks to reporters as he arrives at the office of Sen. Susan Collins, R-Maine, who is moderating bipartisan negotiations on immigration, at the Capitol in Washington. Republicans in Congress have learned to ignore President Trump's policy whims, knowing whatever he says one day he'll change by the next. There's even a name for it: the Tuesday president or the Thursday president, referring to his two-day reversal on immigration. But Trump's decision to impose tariffs is another matter. (AP Photo/J. Scott Applewhite)

FILE - In this Sept. 22, 2005 file photo a steel worker takes a sample at the blast furnace of ThyssenKrupp steel company in Duisburg, western Germany. Ordering combative action on foreign trade, President Donald Trump has declared that the U.S. will impose steep tariffs on steel and aluminum imports, escalating tensions with China and other trading partners and raising the prospect of higher prices for American consumers and companies. (AP Photo/Frank Austin, file)

Traders Gregory Rowe, left, and Michael Milano work on the floor of the New York Stock Exchange, Friday, March 2, 2018. Stocks are opening lower Friday as investors remain concerned that President Donald Trump's plan to impose tariffs on steel and aluminum imports will lead to retaliation from other countries. (AP Photo/Richard Drew)

President Donald Trump speaks during a meeting with steel and aluminum executives in the Cabinet Room of the White House, Thursday, March 1, 2018, in Washington. (AP Photo/Evan Vucci)

FILE - In this file photo taken Wednesday, Dec. 5, 2007, a Chinese worker performs welding work on steel rods using a steel drill at a construction site in Beijing. China has expressed “grave concern” about a U.S. trade policy report that pledges to pressure Beijing but had no immediate response to President Donald Trump’s plan to hike tariffs on steel and aluminum. The Commerce Ministry said Friday, March 2, 2018, that Beijing has satisfied its trade obligations and appealed to Washington to settle disputes through negotiation.(AP Photo/Ng Han Guan, File)

A man walks past an electronic board showing Hong Kong share index outside a local bank in Hong Kong, Friday, March 2, 2018. Asian shares posted steep declines Friday, adding to global stock market losses after President Donald Trump vowed to impose stiff steel and aluminum tariffs, sparking fears of a trade war. (AP Photo/Vincent Yu)

In this Aug. 1, 2016 photo, laborers work in the steel market in Yichang in central China's Hubei province. China has expressed “grave concern” about a U.S. trade policy report that pledges to pressure Beijing but had no immediate response to President Donald Trump’s plan to hike tariffs on steel and aluminum. The Commerce Ministry said Friday, March 2, 2018, that Beijing has satisfied its trade obligations and appealed to Washington to settle disputes through negotiation.(Chinatopix Via AP, File)