Iran's President Hassan Rouhani has registered to run in the upcoming presidential elections in May.

Associated Press journalists watched as Rouhani, 68, registered Friday — the fourth day of the registration period which ends on Saturday evening.

The upcoming vote will be seen, among other things, as a referendum on the 2015 nuclear agreement with world powers, under which Iran agreed to curb its uranium enrichment in exchange for the lifting of international sanctions.

The nuclear deal was engineered by the Rouhani administration and went into effect in 2016. Iran has since resumed selling oil and signed deals worth billions of dollars to replace its aging commercial airline inventory.

Critics of the deal, however, complain that economic benefits have yet to trickle down to average Iranians.