Iran says it will reciprocate if the US returns to its commitments under the June interim deal.
Trump threatens further strikes as Iran warns it will respond to any new attack.
Renewed fighting raises concerns over Strait of Hormuz shipping and global oil supplies.
Iran has called on the United States to honour its commitments under a June interim agreement, saying Tehran would reciprocate, as tensions rose after the first exchange of direct attacks between the two sides since late July and US President Donald Trump threatened further strikes against Iran.
The six-month-old conflict had shifted into an economic standoff before the US attack on Iran's Larak Island on Sunday, with sanctions, blockades and economic pressure increasingly shaping the confrontation. The United States attacked Iran's Larak Island on Sunday, prompting Tehran to launch missiles overnight at two US air bases in Jordan. According to Reuters, oil prices rose on Tuesday after the attacks and reports that two tankers came under fire while leaving the Strait of Hormuz, the global oil supply waterway that Iran has effectively closed to shipping.
Iran points to June interim deal
Iranian President Masoud Pezeshkian said on Tuesday that Tehran would reciprocate if Washington returned to the commitments made under the Memorandum of Understanding (MOU) signed by the two sides in June.
"I am stating clearly that if the U.S. returns to its commitments under the Memorandum of Understanding, the Islamic Republic of Iran will immediately reciprocate," Pezeshkian said.
The MOU declared an end to the fighting but deferred several of the most difficult issues. It also paved the way for a broader 60-day negotiation period, which passed without a further agreement.
Pezeshkian made the remarks in Bishkek, the capital of Kyrgyzstan, during a summit of the Shanghai Cooperation Organisation, whose members also include Russia, China, India and Pakistan.
He had said on Monday that war was in no one's interest and that Tehran remained open to a negotiated solution. However, there has been no sign of a breakthrough.
Tehran has repeatedly said it will allow free navigation through the Strait of Hormuz only if Washington implements the terms of the June MOU.
New exchange raises escalation fears
A senior Iranian source told Reuters that the latest exchanges of fire were a "limited and contained confrontation", but said Tehran would deliver a harsh response if attacked again.
Trump also threatened further action against Iran. "We're going to hit them hard ... There will be a response," a Fox News reporter quoted Trump as telling the channel on Monday.
Trump separately told reporters that the renewed strikes did not signal a return to full-scale war.
While neither side appears to want a return to all-out war, their pledges to respond to further attacks highlight how quickly a conflict that has increasingly been fought through sanctions, blockades and economic pressure could spill back into military action.
The heightened tensions have renewed fears of oil supply disruptions from the world's key crude-producing region. Brent futures rose another 1.3% on Tuesday.
"The tit-for-tat missile exchanges between the US and Iran bring validation to those who believe that even if not a ‘forever war’, this conflict will run and run," said PVM analyst John Evans.
According to Reuters, two supertankers carrying Saudi oil were struck by unknown projectiles within minutes of each other while travelling outbound through the Strait of Hormuz late on Monday. The information came from shipping intelligence and tracking firms Marisks and Kpler.
US steps up economic pressure
Thousands have been killed in the conflict, mainly in Iran and Lebanon, since it began with US and Israeli strikes on Iran on February 28.
Washington has increasingly relied on economic pressure to try to force Tehran to stop blockading the Strait of Hormuz and end the conflict.
US Treasury Secretary Scott Bessent has warned that countries doing business with Iran could face US sanctions. He has also said secondary sanctions are likely to be unveiled weekly as part of efforts to increase pressure on Iran, with an initial focus on banks.
Iranian officials have also pointed to difficulties facing the country's economy. Central bank governor Abdolnaser Hemmati said on Tuesday that Tehran had sufficient foreign currency reserves.
The central bank was ready to inject up to $2 billion into the foreign exchange market to calm recent volatility, Hemmati was quoted as saying by the semi-official Tasnim news agency.
"I am telling the president of the United States: Iran has (foreign) currency and it has enough," he said.
Hemmati's comments appeared partly aimed at reassuring markets after Iranian officials, including Pezeshkian, pointed to growing difficulties for Iran's economy.
Iran's currency plunged to a record low in August, crossing the psychological threshold of 2 million rials to the dollar, while annual inflation reached 66% in July.
