President Donald Trump has demanded a review of the terms of the 2015 Iran nuclear deal, raising concern that Washington might unilaterally pull out of an accord backed by six key world powers.
But on Wednesday the State Department renewed its waiver on the nuclear-related sanctions against the Islamic republic that it had suspended in exchange for Iran submitting to strict controls.
Washington nevertheless maintained a stern tone, imposing new measures to punish Iranian defense officials and a Chinese business tied to Tehran's banned missile program.
And US officials vowed to maintain pressure on Iran over human rights abuses and renewed their demand that Tehran release US citizens held in its notorious jails.
The decision not to renew sanctions came just two days before Iran votes and may prove a boost for President Hassan Rouhani, who approved the nuclear deal and is seeking re-election.
Under the terms of the 2015 deal, the previous US administration of president Barack Obama agreed to waive sanctions on Iran's nuclear program in return for controls to prevent its developing a bomb.
Some of those sanctions waivers come up for review this week for the first time since Trump was elected -- after warning during his presidential campaign that he might rip up the agreement.
But Washington's top diplomat for the Middle East, Stuart Jones, said the department had told Congress that "the United States continues to waive sanctions" that were lifted under the Iran deal.
Nevertheless, his statement added, the Treasury Department will apply new targeted sanctions on individuals and firms helping Iran's banned ballistic missile program.
"Iran continues to pursue missile-related technologies capable of delivering a nuclear weapon," he said, noting that the missile program is in breach of internationally backed UN Security Council resolutions.
"The State Department will continue to partner with our colleagues at the Department of the Treasury to ensure our national security in the face of Iranian threats."
- Political capital -
The Treasury said it had added two Iranian defense officials and an Iranian business to its sanctions lists, accusing them of aiding the missile program or supplying explosives to Syria.
A network of companies controlled by Chinese national Ruan Runling was also added to the list for supplying gyroscopes and other missile-applicable navigation technology to an Iranian firm.
"It is alarming that individuals involved with Iran's missile program are assisting the brutal Assad regime, and we are taking action to curtail this behavior," Treasury Secretary Steven Mnuchin said.
The Trump administration is keen to maintain its tough stance against Iran ahead of the president's visits next week to Tehran's main foes -- US allies Israel and Saudi Arabia.
But Tehran politicians such as Rouhani, who have staked political capital on their engagement with the West delivering economic gains, will be relieved the nuclear accord survives.
Trump has repeatedly denounced the agreement, which was signed in July 2015 by Iran and six major powers -- the United States, China, Russia, Britain, France and Germany.
Critics of the agreement, including Israel, have argued that when some of the terms of the deal expire in 10 and 15 years it will leave Tehran on the threshold of building a bomb.
And in January, just before his inauguration, Trump again dubbed it "one of the worst deals ever made."
Last month, US Secretary of State Rex Tillerson admitted Iran was complying with its own commitments under the deal -- placing its nuclear sites under international scrutiny and halting most enrichment.
But he said Trump had ordered a review of the agreement to determine if it remains in the US interest.