The stalled talks on reviving a 2015 deal to prevent Iran from developing nuclear weapons have revealed tensions between Washington and Tehran as each side attempts to avoid blame if the year-long negotiations collapse.
The talks in Vienna, Austria, stopped last month despite repeated assurances from negotiators including Britain and France that a deal was within reach.
US and Iranian teams voiced mutual mistrust. Iran said any deal should come with a guarantee that a future US leader cannot unilaterally withdraw from it.
Congress appears divided, with many Republicans saying that the deal will not address serious national security concerns including Iran's controversial ballistic missile programme, and what 49 of 50 Republican senators recently called Iran's “ongoing support for terrorism and its gross abuses of human rights".
Tehran says that its nuclear programme is for civilian purposes and its missile strategy or related regional policy should not be part of a nuclear deal.
On Monday, Iranian officials spoke out on social media.
“If there is a pause in the Vienna talks, it is because of the American side has asked for too much,” Iranian Foreign Minister Hossein Amirabdollahian said on his official Twitter account.
“The Ministry of Foreign Affairs acts with power and logic to achieve the highest interests of the nation and to observe the red lines. We will never go overboard with America. If the White House behaves realistically, an agreement is achievable.”
He was referring to US President Joe Biden’s authority to use his veto powers if US politicians block a deal.
Earlier, Saeed Khatibzadeh, Mr Amirabdollahian's spokesman, said that the country's negotiators would not return to Vienna until Washington settles “outstanding issues”.
“If Washington answers the outstanding questions, we can go to Vienna as soon as possible,” he told reporters, without going into detail.
For nearly a year, negotiators from a group of world powers known as the P5+1 — the US, UK, France, China, Russia and Germany — have been working with Iran to restore the deal.
In 2018, it was abandoned by US president Donald Trump, who wanted to negotiate an agreement from scratch.
The original deal sought to limit Iran's stockpiles of enriched uranium, including low and medium-enriched varieties. The latter is easier to highly enrich, which could then be turned into weapons grade material.
These reduced stockpiles and limited enrichment processes would be inspected and verified by UN analysts.
In return, most economic sanctions, except some relating to Iran's support for terrorist groups, would be lifted.
Time is running out
US State Department spokesman Ned Price suggested it was Tehran that could unravel the deal at any point. He said time was running out.
“Anyone involved in the talks knows precisely who has made constructive proposals, who has introduced demands that are unrelated to the JCPOA, and how we reached this current moment,” Mr Price told reporters, using the acronym of the deal which is officially known as the Joint Comprehensive Plan of Action.
“Iran has been able to shrink that breakout time from where it started to a point where we can measure it in weeks rather than months. To us that is unacceptable as a long-term proposition.”
But the deal is not dead.
“We still believe there is an opportunity to overcome our remaining differences,” Mr Price said.
It is not just the US-Iran standoff that complicates matters.
Russia, a signatory to the 2015 deal agreed by the Obama administration, complicated the talks last month with a demand for written guarantees to have broad exemptions from the international sanctions imposed on it because of its invasion of Ukraine, so that it can do business with Iran.
Israel and several countries in the Middle East also have concerns about Iran’s long-range missile and drone programmes, and accuse Tehran of supplying proxy militias in Lebanon, Syria, Iraq and Yemen, including Hezbollah and the Houthis.
The Iran-backed militants have launched attacks against countries from Iraq to Saudi Arabia and the UAE.
Last week, Israeli Foreign Minister Yair Lapid hosted a summit with the leading diplomats of four Arab countries and US Foreign Secretary Antony Blinken.
“This new architecture — the shared capabilities we are building — intimidates and deters our common enemies, first and foremost Iran and its proxies,” Mr Lapid said after the talks alongside his US, Emirati, Bahraini, Moroccan and Egyptian counterparts.
Mr Blinken offered Washington's regional allies reassurance in the event that diplomacy with Iran failed.
“As neighbours and, in the case of the United States, as friends, we will also work together to confront common security challenges and threats, including those from Iran and its proxies,” he said.
In 2020, Iran attacked US troops stationed at Ain Al Asad airbase in Iraq with missiles that caused dozens of concussion injuries.
The attack followed a spiral of escalation between Iran-backed militias and US forces that left one US contractor dead. The US then conducted a drone strike near Baghdad airport that killed a senior Iranian military strategist, Gen Qassem Suleimani, leading to the Iranian attack.
Last month, Iran claimed responsibility for a missile barrage that struck near the US consulate complex in the northern city of Irbil in Iraq Kurdistan’s region, saying it was in retaliation for an Israeli strike in Syria that killed two members of its Islamic Revolutionary Guard Corps.