Dismissing allegations that the plant has a military purpose, Salehi said the facility is being constructed as a "precautionary measure in case of an unwanted incident against our nuclear programme".
He said Iran's nuclear installations are facing "threats every day" and so Tehran "had to take measures to disperse" the locations of its installations.
In the first official disclosure of the plant's location, Salehi said earlier on Saturday that Tehran would allow IAEA inspectors to inspect the plant 100km south of the capital, Tehran, on the road to the city of Qom.
The IAEA said a day earlier that Tehran had written to the agency on September 21 disclosing that it is building a new uranium enrichment facility.
"God willing, this new plant will become operational soon and make the enemy blind," Mohammad Mohammadi Golpayegani, the chief of staff for Ayatollah Ali Khamenei, Iran's supreme leader, said on Saturday.
The announcement of the new facility came just days before an October 1 meeting in Geneva between Iran and six world powers to discuss Tehran's disputed atomic programme.
Mahmoud Ahmadinejad, the Iranian president, denied Tehran was building the plant in secret, as claimed by Western leaders, and told reporters in New York on Friday the facility is "completely legal".
"We actually informed the agency [IAEA] 18 months ahead of time.
"Is this the right thing to do or the wrong thing to do? I thought we are supposed to be encouraged for taking this action."
'Guarantee' for Tehran
Salehi said the plant was a "guarantee" that Tehran's nuclear work would continue.
"Considering the threats [to existing nuclear sites], our organisation decided to do what is necessary to preserve and continue our nuclear activities," he said.
"So we decided to build new installations which will guarantee the continuation of our nuclear activities which will never stop, at any cost."
Obama and other Western leaders have threatened Tehran with new sanctions if it does not "come clean" during the Geneva talks between Saeed Jalili, Iran's senior nuclear negotiator, and representatives of the US, UK, France, Russia, China and Germany.
"They are going to have to make a choice," Obama said at a G20 summit in Pittsburgh, US, on Friday.
"Are they going to go down the path of giving up the acquisition of nuclear weapons and abide by international standards in their pursuit of peaceful nuclear energy, or continue going down a path that will lead to confrontation?" he said.
Uranium enrichment lies at the heart of the nuclear controversy, as the process can be used to make an atomic bomb as well as producing fuel for nuclear reactors.