"Naturally, if we reach the conclusion that (the nuclear deal) is no longer maintaining our national interests, we will put it aside," Ayatollah Ali Khamenei said in a meeting with the cabinet, according to his website.

He said Iran must not "pin its hopes" on Europe, despite European efforts to salvage the nuclear deal following the withdrawal of the United States.

The government of President Hassan Rouhani has been battered by the return of US sanctions, which has triggered a rapid departure of foreign firms and ended his hopes of attracting large-scale investment.

His political enemies are circling, with parliament announcing that two more of his ministers could be impeached in the coming days.

The labour and economy ministers have already been sacked by parliament this month and motions have been accepted to vote on impeaching his industries and education ministers in the coming days.

Khamenei insisted the political tumult was a sign of the strength of Iran's democracy.

He praised the tough questioning Rouhani received in parliament on Tuesday as "a glorious show of the power of the Islamic republic and the self-confidence of officials."

Differences between officials are "natural", he added, though he said they should not be covered by the media "because the people would become worried".

Tuesday's grilling in parliament was the first for Rouhani in five years as president, and lawmakers slammed his handling of five economic issues, ranging from unemployment to the collapsing value of the currency.

In voting at the end of the session, they declared they were unsatisfied with four of his responses.

- 'Day and night' -

Under parliamentary rules, the issues could then have been referred for judicial review, but parliament speaker Ali Larijani -- a close ally of Rouhani -- said on Wednesday there were no legal grounds for doing so.

Parliament can theoretically impeach Rouhani, but he has the protection of Khamenei, who has previously said removing the president would "play into the hands of the enemy".

Instead, Khamenei called on officials to work together "day and night" to resolve the country's economic problems.

Iran's currency has lost around half its value since the US announced it was withdrawing from the nuclear deal in May, and further pain is expected when sanctions on its crucial oil sector are reimposed in November.

Conservative opponents of Rouhani, who have long opposed his outreach to the West, are smelling blood.

Next in their sights is his minister of industry, mines and business, Mohammad Shariatmadari, who is accused of failing to prevent high inflation, particularly in the car industry.

A motion was also filed on Wednesday to vote on the impeachment of Education Minister Mohammad Bathaei, over a series of issues linked to school budgets, the curriculum and alleged mismanagement.