A new underground missile depot is seen in this undated photo released by Iran’s Fars news agency via Reuters.

Pressure is building on the Obama administration to impose new sanctions on Iran after it test-fired two medium-range ballistic missiles within the past three months and flaunted its underground missile storage facilities on national television.

Even Democratic lawmakers who supported the Iran nuclear deal are calling for fresh U.S. sanctions as the Islamic republic embarks on a stepped-up missile program, despite warnings that the measures could derail the landmark agreement’s implementation, which is just weeks away.

Impatience among lawmakers boiled over after the administration notified Congress last week that it would send over a new sanctions package and then said a few hours later that nothing would be coming after all, at least for now. It is unclear how much of the delay was the result of diplomatic calculations vs. routine procedural hurdles.

House Democratic Whip Steny H. Hoyer (Md.), who supported the nuclear deal and now wants more sanctions, said he expects a new package to be presented “in a matter of days, not weeks.”

At the heart of the delay, though, is a dilemma that may become a new norm when the nuclear deal takes effect, as officials must weigh whether more restrictions, or none at all, would produce the worse outcome.

“There are no risk-free options,” said Karim Sadjadpour, an Iran analyst with the Carnegie Endowment for International Peace. “Sanctioning Iran now could unravel the nuclear deal. Yet acquiescing in the face of Iranian provocations could embolden Iran.”

The concern stems from two missile tests Iran announced in October and November. Since then, President Hassan Rouhani ordered the Iranian military to accelerate its production. Brig. Gen. Hossein Salami, who is second in command in the Revolutionary Guard Corps, has boasted that Iran has so many missiles that it doesn’t know where to store them all. And the parliamentary speaker has gone on television touring a new underground bunker called “Missile City.”

The spurt of activity appears to violate an existing U.N. Security Council resolution that explicitly prohibits Iran from anything “related to ballistic missiles capable of delivering nuclear weapons.” Iran insists that it is not a violation, because the missiles have no nuclear warheads.

Under the nuclear agreement finalized with the United States and five other world powers last year, ballistic-missile restrictions will remain in place for eight years.

A new resolution will replace the existing ban, with slightly different language that seems to give Iran more wiggle room. Iran will be “called upon” not to engage in ballistic-missile activity “designed to be capable of delivering nuclear weapons.” It is not clear why Iran did not hold off its missile tests a little longer.

“If they’d waited to test just three more months,” said Greg Thielmann, a fellow with the Arms Control Association, “both Iran and much of the rest of the world would be able to say the Iranians were not really violating it, because the missiles are not designed to be capable of nuclear weapons delivery.”

Iran considers its missile program a defensive counter­measure to a massive supply of weapons being sent to the region, including to rival Saudi Arabia.

In response to fears by Israel, Saudi Arabia and the Gulf emirates that the nuclear deal would allow Iran to extend its influence, the White House promised more than $6 billion in military hardware. Since the talks began in 2013, the United States has provided more than $46 billion in military aid to the region.

The massive military outpouring has fed Tehran’s sense of vulnerability, said Seyed Hossein Mousavian, a former Iranian diplomat now at Princeton University.

“Iran is practically surrounded by countries receiving some of the most sophisticated U.S. conventional arms, and they have to upgrade their capability to keep a balance,” he said. “It is a legitimate security concern.”

Mousavian said he expects that Iran’s missile testing and production will continue. That could present more situations where the White House will have to decide on additional sanctions under U.S. laws and executive orders dating to the 1990s. U.S. sanctions on ballistic missiles will remain in place after the nuclear agreement is implemented, as will those related to terrorism and human rights violations.

With more than 130 individuals and groups already blacklisted over their involvement in Iran’s missile program, it is becoming harder to identify new targets to be sanctioned. North Korea’s underground bomb test added to the workload.

Richard Nephew, a former State Department sanctions expert, said putting together a sanctions case in four or five months is considered rapid.

“I wouldn’t be surprised if a rollout came tomorrow, or in a couple of weeks,” he said. “But a delay — in no way, shape or form — automatically means there was a change of heart and they paused. If this wasn’t so politically sensitive, and so connected to the [nuclear agreement], it wouldn’t even be an issue.”

Many in Congress say it has taken too long already. Seven House Democrats wrote a letter to Obama on Wednesday urging him to act “immediately with punitive measures” against Iran.

“If Iran isn’t held accountable for its actions now, I am concerned they’ll feel emboldened to cheat on their obligations” in the nuclear pact, said Rep. Nita M. Lowey (D-N.Y.), who organized the letter.

Many of the leading voices for new sanctions are lawmakers whose support ensured that the Iran deal survived in Congress.

“I think it’s incumbent on those of us who voted for the agreement but who had great reservations to send a very strong signal to the Iranians that we will not be lulled into a lack of response on other activities which either foment terrorist activity or destabilize the Middle East,” Hoyer said. “We have a responsibility to ensure we don’t send a message of tolerance toward abuse.”