WASHINGTON, Sept 4 (Reuters) - President Donald Trump

said on Thursday his administration would impose tariffs on

semiconductor imports from companies not shifting production to

the U.S., speaking ahead of a dinner with major technology

company CEOs.

Since returning to office in January, Trump's threat of

tariffs has alienated trading partners, stirred volatility in

financial markets and fueled global economic uncertainty.

"Yeah, I have discussed it with the people here. Chips and

semiconductors - we will be putting tariffs on companies that

aren't coming in. We will be putting a tariff very shortly,"

Trump said without giving an exact time or rate.

"We will be putting a very substantial tariff, not that

high, but fairly substantial tariff with the understanding that

if they come into the country, if they are coming in, building,

planning to come in, there will not be a tariff," Trump told

reporters.

Trump has made tariffs a pillar of U.S. foreign policy,

using them to exert political pressure and renegotiate trade

deals and extract concessions from countries and companies that

export goods to the U.S.

"If they are not coming in, there is a tariff," Trump said

in his comments on semiconductors.

"Like, I would say (Apple ( AAPL ) CEO) Tim Cook would be in pretty

good shape," he added, as Cook sat across the table.

iPhone maker Apple ( AAPL ) recently raised its total

domestic investment commitment in the U.S. to $600 billion over

the next four years as tech leaders have warmed up to Trump in

his second term.

Trump said last month that the United States would impose a

tariff of about 100% on imports of semiconductors but it will

not apply to companies that are manufacturing in the U.S. or

have committed to do so.

Taiwanese chip giant TSMC and South Korea's

Samsung Electronics ( SSNLF ) and SK Hynix ( HXSCF ) have

announced investments in chip manufacturing in the United

States.

Trump has faced legal pushback in his use of tariffs. His

administration has asked the U.S. Supreme Court to swiftly hear

a bid to preserve his sweeping tariffs pursued under a 1977 law

meant for emergencies after a lower court invalidated most of

the levies that have been central to his economic and trade

agenda.