Iran has announced plans to establish a new restricted zone in the Gulf in the coming days, saying it will also publish maps for a new shipping corridor through the Strait of Hormuz.
The move appears to be part of Tehran's efforts to increase pressure on Washington in response to the US blockade, as renewed attacks on shipping have pushed oil prices higher.
But where will Iran's new restricted zone be, what could happen to ships entering it and what does the move mean for the already heavily restricted Strait of Hormuz?
Where will Iran's restricted zone be?
The new restricted zone, where Iran says action could be taken against passing ships, would begin where the US blockade of Iran starts and extend into parts of the Gulf.
According to Mohsen Rezaei, secretary of Iran's Supreme National Security Council, it would stretch from an area near the Gulf of Oman and Arabian Sea, through the Strait of Hormuz and into Gulf waters to the north.
Iran has not yet revealed detailed boundaries for the planned zone.
Rezaei said maps would be published showing the shipping routes through the strait that Tehran intends to adopt.
"The maps of the new international corridor, which lies in Iranian and Omani waters and which Iran will manage, have been agreed upon and are due to be signed in the coming days," he said.
Iran and Oman had already agreed in August on a temporary maritime route through the Strait of Hormuz.
Tehran has also previously sought to determine which routes ships can use through the strait. It published a map of approved navigation routes in April, directing vessels closer to the Iranian coast.
Oman, working with the International Maritime Organization, subsequently established a separate southern corridor closer to Oman. Iran's Islamic Revolutionary Guard Corps objected to that route, insisting the Iranian route was the only authorised passage.
The latest Iran-Oman agreement could therefore establish a new recognised route through the strait.
Rezaei's comments suggest that once the agreed corridor is announced, ships travelling through areas outside it could face Iranian sanctions.
What could happen to ships outside the agreed route?
Iran has not yet explained exactly what those sanctions would involve.
Rezaei said any ship entering the new zone could be placed on a sanctions list.
"From now on, if ships are moving on the western or eastern side of the Strait of Hormuz, but stop or commit a violation, we will put them on the sanctions list," he said.
He claimed sanctioned ships could encounter problems obtaining insurance and could face consequences if they attempted to pass through the area again.
"The Strait of Hormuz will become a sanctions zone," Rezaei said.
He did not explicitly say that Iran would militarily attack ships that breached the restrictions.
However, he appeared to hint at the military risks involved, claiming that Iran had tested an anti-destroyer missile over a US warship days earlier.
"This special missile created hell for the Americans, so they fled," Rezaei claimed.
Why is Iran introducing the restricted zone?
Iran says it has been forced to adopt a new strategy on both the war and negotiations following US President Donald Trump's withdrawal from what Rezaei called the "Islamabad understanding".
"After Trump's withdrawal from the understanding, we concluded that we needed to adopt a new strategy regarding the war and negotiations," Rezaei said.
"We considered the US withdrawal from the understanding as putting us on a new path."
The move comes as Washington intensifies its economic pressure on Iran, seeking to restrict the country's oil exports and prevent Tehran from circumventing sanctions.
Iran has increasingly signalled that it could retaliate by targeting US economic and military interests and threatening shipping through the Gulf.
What about the Strait of Hormuz, which Iran says is virtually closed?
Rezaei said Iran would not commit to fully reopening the Strait of Hormuz until the US stopped "sabotage, threats and attacks on Iran".
He claimed the strait was currently effectively closed and described US assertions that it remained open as "completely false".
Before the war, billions of dollars in trade and millions of barrels of oil passed through the waterway each day.
Rezaei claimed that only around seven or eight ships carrying food were now crossing.
He acknowledged that some vessels were still passing through, claiming the US was attempting to move five or six ships at a time near Oman with their tracking systems switched off.
However, independent and Western figures indicate that more ships are still passing through the strait, although traffic remains sharply below pre-war levels.
The UK Maritime Trade Operations centre said on Sunday that 59 ships had crossed the Strait of Hormuz during the previous 48 hours.
Marine analytics firm Kpler, meanwhile, said on Monday that an average of 10 commodity ships per day had crossed over the previous 10 days, the lowest level since May.
Before the US and Israel launched the war on Iran on 28 February, more than 130 ships passed through the strait each day.
The competing figures underline the dispute between Tehran and Washington over how much control Iran currently exercises over the waterway.
How did the conflict reach this point?
The latest developments come around seven months after the United States and Israel launched their war on Iran on 28 February.
A 60-day memorandum of understanding signed in June temporarily halted months of military hostilities, but the arrangement expired last month amid disputes over control of the Strait of Hormuz.
Under the agreement, the US was to end its naval blockade within 30 days, while Iran agreed to clear mines from the strait and allow ships to pass without charge for 60 days.
After a relative pause in military operations during much of August, attacks have resumed.
US Central Command recently said it targeted three Iranian tankers, including one off Kharg Island on Saturday, in response to Iran's Islamic Revolutionary Guard Corps firing ballistic missiles towards two US Navy vessels.
Tehran has demonstrated that it retains the ability to threaten US interests and severely disrupt oil flows through the Strait of Hormuz.
Before the war, around 20% of the world's oil supplies passed through the waterway, making any disruption a significant risk to global energy markets.
Shipping data released on Monday showed an average of just 10 commodity vessels a day passing through the strait over the previous 10 days, the lowest level since May.
Is economic pressure pushing Iran towards tougher measures?
Iran has said it will step up efforts to deal with the economic impact of US sanctions and the blockade.
Three senior Iranian sources told Reuters that it had become increasingly difficult for Tehran to withstand Washington's campaign to choke the Iranian economy by restricting oil exports and preventing sanctions evasion.
Iranian parliament speaker Mohammad Bagher Ghalibaf said on Sunday that the US should understand "before it is too late" that the rules of the conflict had changed.
"From now on, any aggression against Iran's interests and security will be met with a faster, harsher and more painful response," he said.
Ghalibaf said Iran's main struggle, alongside the military front, was now centred on production and people's livelihoods.
He pointed to sharp currency fluctuations, inflation, unemployment and market management as major challenges, saying Iranians could endure hardship but would not tolerate mismanagement or government inaction.
Against that backdrop, Iran's proposed restricted zone appears to be another pressure tool against Washington, linking Tehran's ability to disrupt one of the world's most important shipping routes to the wider military, diplomatic and economic confrontation with the US.