The United States on Monday restored sanctions targeting Iran's oil, banking and transport sectors and threatened more action to stop its "outlaw" policies, steps the Islamic Republic called economic warfare and vowed to defy.

This round of sanction targets over 700 individuals, entities, aircraft and vessels, 50 Iranian banks and subsidiaries, more than 200 persons and vessels in the shipping sector, and targets Iran Air, as well as more than 65 of its aircraft.

The measures are part of a wider effort by US President Donald Trump to curb Tehran's missile and nuclear programs and diminish the Islamic Republic's influence in the Middle East, notably its support for proxies in Syria, Yemen and Lebanon.

The return of the sanctions was triggered by Trump's May 8 decision to abandon the 2015 Iran nuclear deal, which was reached with five other world powers during Democratic President Barack Obama's administration. 

That agreement had removed the many US and other economic sanctions from Iran in return for Tehran's commitment to curtail its nuclear program.

US Secretary of State Mike Pompeo vowed the US would be "relentless" in pressuring Iran.

Speaking before Pompeo, Iranian President Hassan Rouhani accused the United States of targeting ordinary Iranians and said the Islamic Republic would find a way to "continue to sell our oil... to break sanctions."

"The enemy is targeting our economy... the main target of sanctions is our people," he said. "This is an economic war against Iran."

Iranian Foreign Minister Mohammad Javad Zarif said US "bullying" was backfiring by making Washington more isolated, a reference to other world powers opposed to the initiative.

(With inputs from Reuters)