Both the House and the Senate recently passed legislation that would extend the Iran Sanctions Act for ten years, and President Obama is expected to sign it into law. The extension of this act does not automatically impose new sanctions. Rather, it extends the President’s ability to impose sanctions against Iran for the next decade. The US perspective is that continuing to give the president the authority to impose sanctions is a form of leverage against Iran. This leverage is important because there is, and always has been, a concern over Iran’s willingness to cooperate with the nuclear agreement. In January 2016, sanctions against Iran were lifted due to Iranian compliance with measures to curb its nuclear program. But critics of the deal are wary of Iran’s intentions and argue that the US is being too lenient in negotiating with Iran.
The issue here is Iran’s perception of the extension of the Iran Sanctions Act. Tehran considers it a breach of the Iran Nuclear Deal. Part of the agreement was that the US would not impose new sanctions on Iran as long as it adhered to the commitments outlined in the deal. Iran is interpreting the extension of the US President’s authority to impose sanctions for the next decade as a direct violation of the US’s part of the agreement. Iranian officials likely see this as the US preparing to impose sanctions in the future. However, US officials see it as keeping the option open to impose sanctions. The extension of the Iran Sanctions Act does not necessarily mean the US is planning to impose new sanctions on Iran. It does mean that US officials believe it is necessary to keep the option to impose sanctions open in the event that Iran defects from the agreement.
To sum it up, Iran does not need to “firmly respond” to this measure because it is not a violation of the agreement. It is understandable for Iran to feel slighted because the US does not particularly trust it to adhere to the nuclear deal. If a foreign power were to uphold its own leverage against the US after the US was convinced this leverage was gone, the US would similarly feel the need to respond. In this case, however, Iran should have expected the US to extend this authority into the future to maintain its leverage.