Iran is set to block imports of goods from the United States even as decades of heavy sanctions are going to be lifted, following orders from supreme leader Ayatollah Ali Khamenei.

Iran's Ministry of Industry, Mine and Trade is set to follow Khamenei's orders, Iranian media have reported. 

"We will implement the blockade on imports of American goods in a directive," Minister of Industry, Mine and Trade Mohammad Reza Nematzadeh was quoted saying by Press TV.

Ayatollah Ali Khamenei had asked citizens to "be watchful about irregular imports after lifting sanctions and seriously avoid importing consumer goods from the United States" in a post on his website on Sunday, according to The Associated Press. 

He had raised a similar point in a letter to Iranian President Hassan Rouhani after publicly backing the nuclear deal for the first time on 21 October. 

The Iranian leader has long harboured suspicion against the US, which continues despite Iran reaching a historic nuclear deal earlier this year with the United States and five other nations. 

Khamenei's endorsement was the last stage for going ahead with the implementation of the nuclear deal. 

International financial sanctions placed on Iran are likely to be lifted by the end of the year under the agreement, which will also allow inspectors to investigate Iran's nuclear sites. 

Ayatollah Khamenei's warning may have come in the light of a 60% jump in imports from US in the first half of 2015 compared to the first six months of 2014. 

According to The Associated Press, US imports in Iran touched $140 million in the first half of this year.