* Trump threatens tariffs to curb Iran's purchases of

weapons

* US Supreme Court has curtailed Trump's tariff

authorities

* Reuters has reported Iran sought Chinese missiles,

chipmaking tools

(Updates April 8 story with response from China's defence

ministry in paragraphs 12-14)

By David Lawder and Susan Heavey

WASHINGTON, April 9 (Reuters) - U.S. President Donald

Trump said on Wednesday that imports from countries supplying

Iran with military weapons will face immediate 50% tariffs with

no exemptions, threatening the move just hours after agreeing to

a two-week ceasefire with Tehran.

After more than five weeks of strikes against Iran's missile

launchers, military sites and weapons industry, Trump reverted

to tariffs as leverage, using a social media post to warn China

and Russia against restocking Tehran's arsenals.

Beijing and Moscow have denied supplying any weapons

recently, although allegations against Russia have persisted.

But the U.S. Supreme Court stripped Trump of his fastest and

broadest tariff authority, the International Emergency Economic

Powers Act, in February, ruling that his broadest global tariffs

imposed under the 1977 law were illegal.

"A Country supplying Military Weapons to Iran will be

immediately tariffed, on any and all goods sold to the United

States of America, 50%, effective immediately, There will be no

exclusions or exemptions! President DJT," Trump wrote on the

Truth Social site, without naming any countries.

China and Russia have helped Iran build military capacity to

counter U.S. and Israeli pressure, including by supplying

missiles and air-defense systems. That support appeared capped

during the U.S.-Israeli strikes on Iran.

'A CHINA-RELATED THREAT,' LIPSKY SAYS

Reuters reported in February, prior to the first U.S. and

Israeli strikes on Iran, that Tehran was considering a purchase

of supersonic anti-ship cruise missiles from China.

Reuters reported in March that China's top semiconductor

maker, SMIC, had sent chipmaking tools to Iran's

military, according to two senior Trump administration

officials.

"This is a China-related threat, the way I read it. And

China will read it that way," said Josh Lipsky, vice president

and chair of international economics at the Atlantic Council.

Although drone and missile parts routinely flow from Chinese

entities to Iran, evading U.S. sanctions, Lipsky said Trump was

unlikely to follow through with new tariffs in the near term

because that would derail his planned trip to Beijing to meet

with Chinese President Xi Jinping.

China's defense ministry spokesperson Zhang Xiaogang on

Thursday denied reports of Chinese firms providing Iran with

chip equipment and satellite imagery.

"China has always been open and above board on the Iran

issue, maintaining an objective and impartial stance, and has

consistently worked to promote peace talks while never engaging

in any activities that could fan the flames or add fuel to the

fire," Zhang said in a statement.

"The international community can clearly see who is saying

one thing and doing another, and who is creating war and

conflict everywhere."

On Tuesday, U.S. Trade Representative Jamieson Greer said

Trump wanted to preserve stability in U.S.-China ties,

safeguarding U.S. access to Chinese rare-earth minerals while

maintaining prior tariff levels and avoiding a "massive

confrontation" with Xi.

ALTERNATIVE TARIFF TOOLS

Of Trump's still available trade tools, an active "Section

301" unfair trade practices action against Chinese goods from

his first term would be the most likely vehicle for adding new

tariffs quickly, Lipsky said.

A more limited tool would be Section 232 of the Cold War-era

Trade Expansion Act of 1962, aimed at protecting strategic

domestic industries on national security grounds, but it would

limit duties to specific sectors.

Trump's tariffs on Chinese goods over nearly eight years

already have cut U.S. imports from China sharply, from a peak of

$538.5 billion in 2018 to $308.4 billion in 2025, with further

declines in January and February.

Russia has been another source of arms technology for Iran,

but U.S. imports of Russian goods also have shriveled since the

invasion of Ukraine in 2022 and financial sanctions imposed on

Moscow as a result of that move.

U.S. imports from Russia, one of the only countries not

subject to Trump's now-cancelled "reciprocal" tariffs, jumped

26.1% to $3.8 billion in 2025. These imports are dominated by

palladium used in automotive catalytic converters, fertilizers

and their ingredients, and enriched uranium for nuclear

reactors.

The Commerce Department is moving to impose punitive tariffs

on Russian palladium after an anti-dumping investigation.