Iranian officials have complained for months that the Iran Sanctions Act extension amounted to a violation of the P5+1 nuclear deal, and threatened some unspecified retaliation over the matter, which had raised the possibility for Congressional hawks, still looking to derail the nuclear deal, to escalate tensions.
Iranian official, however, say they are going to defuse the tensions over the matter, backing away from the threat of retaliation, though they continue to express annoyance the extension of the Iran Sanctions Act. They tried to reassure Russian officials that they won’t imperil the deal over the matter.
The Iran Sanctions Act doesn’t in and of itself technically violate the letter of the P5+1 deal, since it does not impose any new sanctions on Iran. Rather, the act makes it easier for future presidents to unilaterally reimpose sanctions, which would themselves be violations of the deal.
Either way, there seems to be considerable effort internationally to make it clear the US does not have the ability to unilaterally destroy the pact, which was agreed up by 7 nations, and Iran is likely facing pressure not to rock the boat, and to let the international community handle any US moves on the deal.