"The date has been set, but the negotiations for the venue are still ongoing," Salehi told AFP.
"Turkey has announced its readiness to host the talks, and my personal priority is Istanbul," he added.
The talks carry hopes of defusing a tense international showdown over Iran's nuclear activities that has sent oil prices soaring.
Israel has brandished the threat of possible military action against Iran's nuclear sites, while the United States has put its energies into sanctions and diplomacy but has not ruled out the military option.
Salehi made his announcement as he welcomed Turkish Prime Minister Recep Tayyip Erdogan to Tehran for a two-day visit focusing on Iran's nuclear programme and bilateral ties.
On Erdogan's arrival, Salehi told the official Islamic Republic News Agency that the next round of the talks between Iran and the so-called P5+1 group comprising the United States, Russia, France, Britain, China and Germany would take place on April 13.
Speaking to AFP, Salehi said that a "suggestion" from the P5+1 for a venue had been received and was being studied, and that the location "will be announced soon."
He did not say what venue had been proposed by the world powers.
The last round, held in Istanbul in 2011, ended in failure. The round before that, in 2010, was in Geneva.
In Brussels, a European diplomat confirmed to AFP that the next round of negotiations would start on April 13 but that a location had not yet been agreed.
Turkey's ambassador to Tehran was quoted by Iran's Press TV as saying: "Turkey stands ready to host the talks between Iran and the P5+1 group, but everything depends on an agreement between Iran and the P5+1."
Erdogan arrived in Tehran from South Korea, where he had attended a nuclear security summit with other world leaders including US President Barack Obama.
Salehi did not directly respond to an AFP question about whether Erdogan was carrying any message from Obama to Iran's leaders, saying: "So far we've only talked about bilateral issues."
Obama on Monday warned in Seoul that "time is short" for a diplomatic solution to the standoff with Iran.
"Iran must act with the seriousness and sense of urgency that this moment demands," he said.
Erdogan, who was accompanied by several key ministers and intelligence and military officials, was to meet Iranian President Mahmoud Ahmadinejad and supreme leader Ayatollah Ali Khamenei during his visit, Iranian officials said.
Turkey relies on Iran for 30 per cent of its oil imports, and has refused to go along with sanctions imposed by the United States and Europe, saying it will observe only UN-mandated restrictions on Iran.
However, Turkey is also a NATO member, and it has agreed to deploy parts of an anti-missile shield that could be used against Iran, a point that has generated friction in the past with its neighbour.
The two countries are heavyweight players in the Middle East.
They hold different positions on several issues, notably on Syria. Ankara wants to see Syrian President Bashar al-Assad step down as part of a solution to the crisis there, while Tehran is giving Assad political and material support.
Salehi said Iran-Turkey trade currently amounted to $16 billion a year but could reach $30 billion by 2015.
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