Araqchi said in a post on X the strait was open for all commercial vessels for the remainder of the US-brokered 10-day truce between Israeli forces and Iran-aligned Hezbollah agreed on Thursday between Israel and Lebanon.
A senior Iranian official told Reuters that transit would be through designated lanes that Iran deemed safe for navigation and would exclude naval vessels.
The US-Israeli conflict with Iran, which started on February 28, has killed thousands of people and destabilised the Middle East.
The conflict also largely closed the Strait of Hormuz, through which a fifth of the world's oil and liquefied natural gas usually transits, threatening the worst oil shock in history.
Oil prices fell by 11 per cent, extending earlier losses, following Araqchi's post.
Major shipping companies reacted more cautiously, signalling it may take more time for traffic through the choke point to return to normal levels, which was about 130 ships a day prior to the war.
German shipping company Hapag-Lloyd said it would refrain from passing through the strait while it assessed the announcement and the Norwegian Shipowners' Association said several factors needed to be clarified, including the possible presence of sea mines.
Trump expressed his thanks for the reopening on TruthSocial, saying the strait "is fully open and ready for full passage".
However, Trump said the US military blockade of ships sailing through the strait to Iranian ports - announced after talks with Iran last weekend in the Pakistani capital Islamabad ended without agreement - remained in place.
He said that blockade would remain in full force until "our transaction with Iran is 100 per cent complete," which he said should happen very quickly given that most points were already negotiated.
A Pakistani source involved in mediating between the US and Iran said on Friday there was progress in backdoor diplomacy and that an upcoming meeting between the two sides could result in the signing of a memorandum of understanding, followed by a comprehensive deal within 60 days.
"Both sides are agreeing in principle. And technical bits come later," the source said on condition of anonymity.
French President Emmanuel Macron and UK Prime Minister Keir Starmer welcomed the announced reopening of the Strait of Hormuz but said it must become permanent.
The two said they will keep planning an international mission to restore maritime security, with a meeting of military planners in London next week.
Speaking after a gathering of 50 countries, Macron said, "We all demand the full, immediate and unconditional reopening of the Strait of Hormuz by all parties".
The US-backed ceasefire agreed between Israel and Lebanon to end the fighting between Israel and Hezbollah appeared to be largely holding on Friday despite some Lebanese army reports of violations by Israel.
There was no immediate comment from the Israeli military on the reported ceasefire violations on Friday.
Trump said on Friday that the United States has banned Israel from further bombing in Lebanon.
"Israel will not be bombing Lebanon any longer. They are PROHIBITED from doing so by the U.S.A. Enough is enough!!!" Trump said in a social media post.
with AP
