On Wednesday, one year after the U.S. announcement of withdrawal from the 2015 Joint Comprehensive Plan of Action (JCPOA) and the resumption of sanctions, Iranian President Hassan Rouhani announced that Iran would reduce its commitments but would not withdraw from the nuclear deal.

Iran’s response was carefully calibrated and demonstrated considerable restraint. Highlighting Iran’s continued commitment to the deal, Rouhani stated that Iran would give remaining parties to the deal 60 days to uphold their end of the bargain before Iran would be forced to walk away. The president’s statement was reiterated in a letter sent by the Supreme National Security Council — a body that makes decisions based on consensus within the diplomatic and security circles — to the other states party to the nuclear deal.

Why Iran was boxed in

Iran’s move was a response to a year of increasing struggles with renewed sanctions, a new set of U.S. sanctions and several provocative U.S. threats.

On April 8, President Trump designated Iran’s Islamic Revolutionary Guard Corps as a foreign terrorist organization, increasing the risk of potential confrontation between U.S. troops and Iranian forces or proxies in the region. On April 21, the administration announced an end to waivers that allowed eight countries to purchase Iranian oil and funnel the money into escrow accounts to be used for the purchase of humanitarian goods. While countries may still be determining how to respond to this, Iran’s oil shipments have tumbled. And each successive measure was accompanied by tough rhetoric and threats, calling on Iran to cease its nefarious activities and give in to Secretary of State Mike Pompeo’s 12 demands. Importantly, last week, the administration framed a routine deployment of aircraft carriers, announced last month, to the Persian Gulf as intended to ‘send a clear and unmistakable message’ to Iran. This only serves to heighten tensions.

On May 3, the Trump administration revoked two waivers allowing Iran to ship excess heavy water to Oman and trade excess enriched uranium for low enriched uranium with other countries. This effectively limits Iran’s ability to continue implementing its commitments under the deal. It also announced that waivers to continue the conversion of three Iranian facilities — Bushehr nuclear power plant, the Arak heavy water reactor, and the Fordow enrichment plant — would be renewed, for 90 days.

U.S. withdrawal from the nuclear deal and the ratcheting up of pressure made implementation of the deal difficult for the countries which remained committed to the JCPOA. They feared the United States would directly impose sanctions on anyone who dealt with Iran. This made them dependent on U.S. waivers allowing them to buy Iranian oil or continue working on the conversion of Iran’s nuclear program, as per the terms of the deal. But over the past few weeks, Trump has progressively closed off all these avenues.

Iran had limited options

Iran had few options. Going back to the U.N. Security Council would run the risk of invoking ‘snapback’ sanctions, which would be universally applied and thus more effective and harmful than unilateral U.S. sanctions. It also did not want to simply walk away from the deal: Iranians and their officials suffer from nuclear fatigue, and few want to rehash this issue over and over again.

The Rouhani administration does not want to risk losing international support for their continued implementation of the deal. Iran has been highly pragmatic and strategic in its approach to keeping the deal alive. It understood that certain measures would immediately be viewed as ‘significant violations’ of the deal, inviting further sanctions, such as restricting access to their facilities by IAEA inspectors or resuming enrichment at the Fordow underground facility.

But it also couldn’t sit by and continue to uphold its commitments under the deal, while the United States increased its effort to punish Iran. As a result, Iran reacted in a limited manner, and in direct reaction to the Trump administration’s announcement that some nuclear waivers would not be renewed.

How Iran responded

Iran’s announcement was a direct reaction to these new restrictions. Headlines suggesting that Iran had left the nuclear agreement were misguided. Rouhani said that Iran would no longer ship its excess low enriched uranium and heavy water abroad. This bought Iran some time — several months in fact — given that the February IAEA report stated that Iran had 124.8 metric tons of heavy water, well below the 130-ton cap, and 163.8 kilogram of uranium equivalent, also well below the 202.8 kg (equivalent to the 300 kg cap for low enriched uranium).

Rouhani gave other states party to the deal 60 days to facilitate the promised economic dividends of the deal for Iran, after which Tehran threatened to resume enrichment beyond 3.67 percent and construction at Arak. Iran chose the 60-day deadline because article 36 of the Iran deal states that the snapback mechanism and resumption of UN Security Council resolutions occur after 65 days, giving Iran an additional five days to consider whether to enact their threats should their terms not be met.

Importantly, both these measures are reversible and sit in the gray area of the Iran deal. As such, Tehran is not in breach of the deal. Rouhani was at pains to highlight this in his remarks, stating that Iran was ‘diminishing its commitments’ and not withdrawing from the deal. Neither measure puts Iran on the path to a nuclear weapon, but they slowly chip away at the constraints established by the 2015 nuclear deal. Iran also outlined a general road map to avoid a worsening of the situation in a letter to its European counterparts, which Secretary Pompeo referred to as ‘intentionally ambiguous’. Tehran called on the remaining five countries party to the deal to help protect Iran’s interests in oil and banking sectors.

Iran’s announcement on scaling back its commitments isn’t surprising. What is surprising is that it took Iran this long to announce it. Iran had been implementing the nuclear deal for the past year, but it continued to face increasing pressure from the United States. The Trump administration’s ‘maximum pressure’ campaign denied — and continued to deny — Iran any benefits from the deal. That is what drove the leadership in Tehran to take these retaliatory steps.

Dina Esfandiary is an International Security Program Research Fellow at the Harvard Kennedy School’s Belfer Center for Science and International Affairs and a Fellow in the Middle East department of the Century Foundation.