US Treasury slaps punitive sanctions on Turkey's defence minister

US President Donald Trump on Monday authorized sanctions on Turkey's leaders, reimposed steel tariffs and ended talks on a trade deal, seeking to punish the historic ally for its deadly offensive into Syria.

Trump also said he was reimposing tariffs of 50 per cent on Turkish steel -- one of a series of measures taken last year to win the release of a detained US pastor, and which contributed to a plunge in the value of the country's lira currency.

In May, Trump reduced tariffs back to 25 per cent, in line with levels the protectionist-minded president has imposed on other trading partners including the European Union.

The US Treasury also slapped punitive sanctions on Turkey's defence minister and two other ministers.

Minister of Defense Hulusi Akar, Interior Minister Suleyman Soylu, and Energy Minister Fatih Donmez were placed on the Treasury's sanctions blacklist, freezing their US assets and banning US or US-related transactions with them.

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The defence and energy ministries were also hit with sanctions, the Treasury said.

"The United States is holding the Turkish government accountable for escalating violence by Turkish forces, endangering innocent civilians and destabilizing the region," said Treasury Secretary Steven Mnuchin.

The sanctions seek mainly to lock the designated individuals and organizations out of the global financial system, by threatening to penalize any international banks with a US presence involved in transactions with those on the blacklist.