A group of Iranian reformist activists and former officials have urged UN Secretary General Antonio Guterres to encourage Washington to return to the nuclear deal with Iran and lift the sanctions that have paralyzed its economy.

The letter signed by 17 former officials including former government spokesmen Abdollah Ramezanzadeh and Behzad Nabavi and former Presidential aide Shahindokht Molaverdi blames the U.S. pull-out from the nuclear deal as the cause of mounting tensions in the Persian Gulf region and lashes out at the Trump administration for its "unilateral" decision and violation of a deal made by its predecessor.

The anti-US tone of the letter may indicate that the signatories possibly issued the statement to please Iran's Supreme Leader Ayatollah Ali Khamenei, hoping it can pave their way back to the forefront of Iranian politics after years of being sidelined by Khamenei's conservative allies.

The letter, written more than a year after Trump left the nuclear deal with Iran, says the U.S. pull-out "propels the world into a new era where international pacts are no longer binding," adding that "It is UN's responsibility to take due measure against this fundamental violation of its charter."

The letter accuses U.S. and Israel of starting a war against Iran and calls on Guterres to encourage the U.S. "to return to the nuclear deal with Iran, lift sanctions and stop adventurism in the region."

Other signatories of the letter include, former Tehran City Council member and intelligence officer Saeed Hajarian and prominent columnist Abbas Abdi.