"I have just authorised a doubling of Tariffs on Steel and Aluminum with respect to Turkey as their currency, the Turkish Lira, slides rapidly downward against our very strong Dollar!" Trump said on Twitter.
"Our relations with Turkey are not good at this time!" Trump's announcement came as Turkey's embattled lira hit new record lows against the US dollar and euro, losing nearly nine percent in value as strains with the United States showed no sign of abating and fears grew over the exposure of European banks.
Turkey remains at loggerheads with the United States in one of the worst spats between the two NATO allies in years over the detention for the last two years of American pastor Andrew Brunson and a host of other issues.
Washington this month imposed sanctions on senior Turkish officials, angering President Recep Tayyip Erdogan and prompting retaliatory measures by Ankara.
Meanwhile, markets are deeply concerned over the direction of economic policy under Erdogan with inflation at nearly 16 percent but the central bank reluctant to raise rates in response.
Erdogan today called on Turks to support their struggling currency.
"We will not lose the economic war," state-run TRT Haber television quoted Erdogan as saying.
"If you have dollars, euros or gold under your pillow, go to banks to exchange them for Turkish lira. It is a national fight." Harsher US tariffs were likely to punish Turkey's already faltering steel exports to the United States.
In the first three months of 2018, Turkish steel exports to the United States fell nearly 50 percent over the same period in 2017, making it the only top 10 source of US steel imports to see a decrease, according to the US Commerce Department.