What are Iran's options to escalate further in face of US economic threats?

US threats to impose the "toughest sanctions in history" to force Iran to buckle to its demands after nearly six months of war have raised the prospect of a new round of escalation in the Gulf.

How could Iran respond to the economic pressure?

Can Iran stop more oil getting out of the Middle East?
Mohsen Rezaei, the former Revolutionary Guards chief and secretary of Iran's Supreme National Security Council, has already threatened to shut down oil exports — one of Tehran's main strategic approaches since the war began on 28 February. "If the economic war continues, not a single drop of oil will be exported, neither through the Strait of Hormuz nor from anywhere in the Persian Gulf," he said.

Iranian attacks and threats to shipping have already stopped most traffic through the Strait of Hormuz, largely shutting down a waterway that carried around a fifth of global energy before the conflict.

Although some oil tankers have been moving through the strait in recent weeks, volumes remain very low and on Sunday (23 August) Iran blacklisted 45 tankers it says failed to comply with the rules it wants to impose on Hormuz shipping.

Missile, drone or speedboat attacks on tankers trying to leave the Gulf have repeatedly pushed up oil prices during the six months of the conflict. Meanwhile, Tehran's Houthi allies have restricted Red Sea shipping with attacks and threats to blockade all Saudi Arabian shipping, which carries crude to Asia through the Bab el-Mandeb strait past the group's Yemeni stronghold.

While the attacks initially only stopped some vessels, with more than half still getting through in mid-August, the situation is difficult for shippers, with Chinese shipping companies now rerouting away from Bab el-Mandeb, according to industry sources.

Further attacks, such as the one that targeted a vessel off the main Saudi Red Sea oil terminal at Yanbu on Monday or a drone strike near the Suez Canal in early August, could raise oil market anxiety levels and crude oil prices.

Are Gulf states still at risk of Iranian attack?
Iran has threatened to retaliate against any neighbours who take part in US efforts to strangle the country's economy with "earthquake" force. It has targeted Gulf states and Jordan repeatedly during the war, mostly focusing on US bases but also hitting energy infrastructure and other targets.

Any intensified attacks that targeted upstream oil or gas facilities could further drive up energy prices in ways that inflict political damage on the Trump administration and could be harder to reverse than attacks on shipping.

Targeting power and water desalination plants in the hot, parched region would also pose a major risk to US-aligned Gulf monarchies that function as significant financial hubs for the global economy.

Can Iran attack Western countries directly?
While Western countries are beyond the range of Iran's main munitions, the Revolutionary Guards have historically been willing to find alternative ways of attack.

On Monday, Britain said Iran-linked hackers had shut down a small electricity station while US officials said Tehran was likely behind cyber attacks on water plants in Minnesota. Iran has not commented on those allegations. Western security services have also accused Iran of recruiting local people to stage attacks or attempt assassinations in the West. Iran has denied that.