The United States unilaterally proclaimed on Saturday that UN sanctions against Iran are back in force and promised to punish those who violate them.
"Today, the United States welcomes the return of virtually all previously terminated UN sanctions on Iran," US Secretary of State Mike Pompeo said in a statement.
He said the measures were "back in effect" from 8:00 pm Washington time (0000 GMT Sunday).
The government of US President Donald Trump also promised to "impose consequences" on any UN member state which does not comply with the sanctions.
The threat is formidable: those deemed to be in defiance by Washington will be denied access to the US financial system and markets.
"If UN member states fail to fulfill their obligations to implement these sanctions, the United States is prepared to use our domestic authorities to impose consequences for those failures and ensure that Iran does not reap the benefits of UN-prohibited activity," Pompeo stated.
The White House plans to issue an executive order on Monday spelling out how the US will enforce the restored sanctions, and the State and Treasury departments are expected to outline how foreign individuals and businesses will be penalized for violations.
With 45 days to go until the November 2 election, Trump could unveil those measures during his speech at the UN General Assembly on Tuesday.
The sanctions were lifted in 2015 when Iran signed on to an international agreement not to seek to build nuclear weapons.
But Trump said that the accord, negotiated by his predecessor Barack Obama, was insufficient and withdrew the US from the agreement in 2018, then renewed and even strengthened Washington's bilateral sanctions.