Speaking to Al Jazeera, Arron Reza Merat, a London-based Iran analyst, said that while Rouhani's victory maybe a reflection of the increasing influence of reformists, second-term presidents in Iran "do turn into lame ducks", and that the supreme leader and the security establishment have "larger sway" in the country.
The deal with the US, France, Germany, Britain, Russia and China included rolling back part of Iran's nuclear program in exchange for the lifting of certain financial and economic sanctions.
In a meeting with Mogherini prior to the ceremony, Foreign Minister Mohammad Javad Zarif said the European Union needs to be "alert" to Trump's efforts "to undermine the deal laying the blame on Iran".
Iranian officials have said the high turnout expected at President Rouhani's second inauguration would send "an important message" to the world, especially at a time when the United States has sought to stir world opinion against the country.
Last month the United States announced new sanctions against entities and individuals with ties to Iran, a day after certifying the Iranian government's compliance with the nuclear agreement.
Iran said Thursday that new USA sanctions were a violation of its nuclear deal with world powers, piling pressure on President Hassan Rouhani as he starts his second term.
"Iran has proved that it will respond to respect with respect, and to sanctions and threats with an appropriate response and with resistance", he added.
Rouhani was first elected in 2013 with almost 51 percent of the vote.
Amnesty International recently released a 94-page report entitled "Caught in a Web of Repression - Iran Human Rights Defenders Under Attack", which detailed the situation for those in Iran who stand up for human rights against the regime.
The EU's foreign policy chief Federica Mogherini attended the inauguration along with several other foreign guests, including French and German officials. Further complicating matters, US President Donald Trump has openly discouraged foreign investment in Iran and signed new sanctions on Wednesday. "We prefer peace to war and reform to rigidness", said Rouhani.
On Afghan migrants living in Iran, Dr Rouhani also said: "With regard to the serious resolve by the governments of Iran and Afghanistan, the issue must be resolved".
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