From the Gulf states to Türkiye and Pakistan, Iran's neighbours know well the risks that US strikes targeting the Islamic republic would entail, from regional conflagration to waves of migration.
AFP looks at the potential regional impacts of any escalation.
The main concern of Washington's allies in the Gulf is Iranian retaliation.
Even though they benefit from US protection, they host American military sites that could be targeted by Iranian counter-strikes. In June, during the 12-day war with Israel, Iran fired missiles at the Al Udeid US military base in Qatar, the biggest in the region.
Qatar joined Saudi Arabia and Oman in urging US President Donald Trump's administration to postpone strikes on Iran, a Saudi official told AFP on Wednesday.
Despite being weakened by the war with Israel, Iran remains a potent threat. The worst-case scenario for the Gulf states, although it does not appear imminent, would be direct targeting of their infrastructure.
The Gulf states "know they are vulnerable because the Iranians have enough basic intermediate-range missiles to hit their vital infrastructure -- desalination plants, hydrocarbon hubs, power stations," Pierre Razoux, director of studies at the Mediterranean Foundation for Strategic Studies (FMES), told AFP.
"Without this infrastructure, these hot desert countries risk becoming unliveable," he said.
The oil-producing states of the Gulf also fear that strikes would result in a blockade of the key Strait of Hormuz, the chokepoint through which 20 percent of the world's oil supply flows, said Cinzia Bianco, a Gulf researcher at the European Council on Foreign Relations (ECFR).
The Gulf Cooperation Council (GCC) countries are pursuing costly political agendas -- changing their economic models, undergoing major construction projects and energy transitions.
"For all of the GCC countries a liquidity crisis would be a big problem. They are in a big spending time," Bianco said.
"All of that is more complicated if there is a weaker Iran" and an oil and economic crisis.
"So if they have to mind the security spillover of a collapse of the regime, that adds another layer of complexity."
A drop in Gulf supplies could prompt China, the world's top oil importer, to fill the gap elsewhere, Razoux said.
Upheaval in Iran would risk rekindling other conflicts that Tehran could reactivate in reprisal, through the Houthis in Yemen or Hezbollah in Lebanon.
A weakened Iran could also give free rein to groups hostile to its neighbours such as Türkiye or Pakistan.
"Chaos on the borders, more refugees into Türkiye, which Türkiye cannot afford, and the PKK-linked groups getting more active," Gonul Tol of the Middle East Institute said.
Pakistan reiterated on Thursday that a stable and peaceful Iran is in Islamabad's interest.
"Any US military attack on Iran would have dangerous destabilising consequences for the entire region," former diplomat and political analyst Maleeha Lodhi told AFP.
"Pakistan in particular would be seriously affected if there is a spillover across its border.
"Any ungoverned space opening up near its border would strengthen militants in its restive province of Balochistan and pose a grave security threat to Pakistan."
Some of Iran's neighbours also fear significant population movements or an influx of refugees, such as Türkiye experienced during Syria's civil war.
"With Iran, the cross-border shocks are likely to be an order of greater magnitude given the size, population, heterogeneity of the country," said Carnegie Europe's Sinan Ulgen of the country of 92 million inhabitants and multiple communities.
"So this is the scenario that Türkiye would want to avert."
Baku-based Russian analyst Nikita Smagin told AFP: "Countries like Armenia and Azerbaijan fear it because it can... threaten the stability of the whole country easily."
