The United States agreed Thursday to continue for now to exempt Iran from nuclear-related sanctions but slapped new measures on targets accused of cyber attacks or destabilizing the region.
The decision to continue to waive the sanctions was expected, but the new sanctions and some tough words from President Donald Trump will be seen as a victory for opponents of the Iran nuclear deal.
Trump is due to decide before October 15 whether Iran has breached the 2015 nuclear agreement, and critics fear he may abandon an accord they think prevents Tehran from building a nuclear bomb.
"You'll see what I'm going to be doing very shortly in October," Trump told reporters traveling with him on Air Force One. "The Iran deal is one of the worst deals I've ever seen.
"Certainly at a minimum the spirit of the deal is atrociously kept. The Iran deal is not a fair deal to this country. It's a deal that should not have ever been made."
Policy hawks welcomed the US Treasury's announcement of new sanctions on non-nuclear issues, and officials were at pains to show they had waived nuclear sanctions only grudgingly.
"The administration did approve waivers in order to maintain some flexibility," State Department spokeswoman Heather Nauert said.
A senior administration official, speaking on condition of anonymity, called the waiver "a holding action."
"This is the action that the US is taking in the interim," he said, "while the president and his cabinet come to a final decision in consultation among themselves and in consultation with allies."
The 2015 Iran deal, approved by Trump's predecessor Barack Obama, was implemented under a Joint Comprehensive Plan of Action, or JCPOA, and enshrined in UN Security Council Resolution 2231.
Under the JCPOA, Iran surrendered much of its enriched uranium, dismantled a reactor and submitted nuclear sites to UN inspection, while Washington and Europe lifted some sanctions.
The International Atomic Energy Agency (IAEA) says that Iran has lived up to the terms of the nuclear agreement, but Washington and its allies have been angered by Tehran's other actions.
Tehran continues to develop and test ballistic missile technology banned under previous UN resolutions, and its Revolutionary Guard Corps supports militias in Syria, Iraq, Lebanon and Yemen.
Trump has declared the deal a disaster and there are growing signs that next month he may declare that he thinks Iran has broken its promises -- opening the way to new US sanctions.
US Secretary of State Rex Tillerson, speaking in London, said Trump would "take into account the totality of Iranian threats, not just Iran's nuclear capabilities."
He argued that the JCPOA expects the signatories to "positively contribute to regional and international peace and security.
"In our view, Iran is clearly in default of these expectations," he added speaking alongside British foreign secretary Boris Johnson.
Tillerson noted that Iran continues to support Bashar al-Assad's brutal regime in Syria, to develop ballistic missiles and to carry out cyber attacks -- threatening Middle East security.
But Iran's foreign minister, Javad Zarif, insisted that Tehran would not be bullied into renegotiating the JCPOA, tweeting: "A 'better' deal is pure fantasy. About time for US to stop spinning and begin complying, just like Iran."
In Washington, some observers welcomed Trump's tough talk.
Mark Dubowitz, CEO of the Foundation for Defense of Democracies, which has long criticized the Iran accord, has dubbed the approach of keeping the deal's relief while imposing new measures "waive-and-slap."
"It is the first step in a process under which the contours of the administration's pressure campaign will come into sharper relief."
But the former Obama administration officials who negotiated the deal issued a stark warning that if Trump declares Iran to be in violation of the deal it could collapse.
This could alienate the powers that co-signed the accord -- Britain, China, France, Germany and Russia -- and allow Iran to quickly resume the quest for a viable nuclear weapon.
And this would undermine America's credibility as it attempts to cajole North Korea into giving up its own nuclear arsenal.
Former senior White House official Colin Kahl said Iran could have enough enriched fuel for a bomb within a year of the deal collapsing, dubbing the Trump policy a "train wreck."
"You won't have a diplomatic option because in the event that we get blamed for blowing up the deal we won't be able to reconstitute international consensus," he said.
"And as the guy who used to have oversight for war plans against Iran in the Obama administration, I can tell you that there's no military option that buys you a fraction of the time that this deal does, or a fraction of constraints.
"So it puts the United States in a terrible position of an almost inevitable march to war at great distraction from every other challenge we face, to include North Korea but also China and Russia, and everything else. It's just completely unnecessary."
Th US Treasury imposed economic sanctions on 11 individuals and companies accused of supporting Iran's Revolutionary Guards or engaging in cyber attacks against US banks.
These targeted an engineering company, two air transport firms and an IT company accused of carrying out denial-of-service attacks on at least nine American financial institutions.