"I drank the cup of poison," late Iranian Supreme Leader Ayatollah Khomeini said in June 1988 upon signing the UN truce deal that put an end to eight disastrous years of war with neighbouring Iraq.
With those words, Khomeini inked Iran's first agreement after the 1979 Islamic Revolution.
Following the revolution, Iran not only entered a war with Iraq, but its relations with the international community were badly affected, especially after Khomeini called the US "The Great Satan" and threatened to destroy Israel.
The United States was one of Iran's key allies during era of Shah Mohamed Reza Pahlavi until 1979, and in the late 1950s Iran's Shah and the US cooperated in the area of nuclear energy production.
Since the revolution relations between the Islamic Republic and the US have gone from bad to worse.
A sudden shift
"The United States and Iran have a real desire to reach a nuclear agreement because this is the first time in the 36-year-old history of the Islamic Republic that they have had face to face talks," Holly Dagres, a Middle East analyst, told Ahram Online.
Dagres explained that Iran has been isolated for a long time and “has no need to appease the West."
"The ardent work put forth by the Iran nuclear negotiating team demonstrates Tehran means business and shares a respect for international law, or else they would've walked away from the table a while ago," she added.
A year and four months have passed since the US and Iran announced the beginning of the first official nuclear talks alongside China, Russia, France, Germany and UK, but a framework must be reached within the next few days.
In November 2013, Iran agreed along with the P5+1 to start negotiations over a deal that will commit Iran to freezing its nuclear project and decrease the number of centrifuges by 40 percent, as well as helping Iran by lifting some of the international sanctions imposed on it by the United States.
The talks' deadline has been extended three times.
In November 2013, the talks were set to finish in June 2014, but when an agreement was not reached they extended the talks to 24 November 2014. However, before the deadline another seven months of talks were announced with an obligation to seek a framework by the end of March, and then resume negotiations until June 2015 when a lasting agreement would be signed.
What are the negotiations for?
The US and its other five partners are trying to limit the number of Iranian centrifuges by 40 percent, which are believed to have passed 10,000, freeze Iran's nuclear enrichment programme for ten years and put all reactors and nuclear plants under the inspection of the International Atomic Energy Agency (IAEA). Demands went as far as asking Iran to eliminate most of its fuel stockpiles to prevent the production of nuclear weapons.
All the way through negotiations Tehran has denied it is planning to develop nuclear weapons and asserted that nuclear plants are only meant for energy and medical purposes.
"Iranians will not completely stop enriching uranium. Even if (Iranian President Hassan) Rouhani's administration wanted to do this, it would be politically damaging," Geneive Abdo, a fellow at Stimson's Middle East programme and a non-resident fellow at the Brookings Institution, told Ahram Online.
Abdo explained that lifting sanctions is Iran's main goal. "Iran cares much less about ending its isolation, although a large part of society there would like to be re-integrated into the world community," Abdo said.
Majid Rafizadeh, an Iranian-American columnist and a member of Harvard International Review's advisory board, sounded very skeptical about Iran's nuclear facilities being fully inspected. "The Islamic Republic has a history of not disclosing nuclear sites to the IAEA and violating the Non-Proliferation Treaty (NPT). It depends on how inclusive the inspections will be."
"Nevertheless I believe Iran will be the main winner if this agreement is concluded; sanctions will be removed and Iran will continue its nuclear programme without any concrete restrictions after ten years," Rafizadeh said.
What if the deal fails?
Despite optimism by most experts regarding a deal, others warn that more sanctions will likely be imposed if no agreement is reached.
"If a nuclear deal was to fail, more sanctions would further pinch the Iranian economy," Dagres said.
"However, sanctions are not something Iran's government, or people cannot withstand," Dagres added.
The US and its western allies enforced sanctions on Iran, stopped trade relations and froze assets and bank accounts after the 1979 seizure of the US embassy in Iran and the taking of 52 American hostages.
Sanctions were also meant to prevent any further progress in Iran's nuclear activities, according to the US State Department.
"For 36 years, the Islamic Republic of Iran has been sanctioned and managed to thrive through black-markets and trade with so-called black knights, i.e. Eastern European countries like Belarus, Hungary, and Romania. The Iranian people thrived under much worse circumstances during the Iran-Iraq war,” Dagres said.
On the other hand, Rafizadeh, an Iranian-American political columnist, believes that more sanctions will not be imposed. "I believe both sides might stick to the interim deal and avoid a further escalation of tensions."
"We shouldn't let such a chance slip away," Iranian President Hassan Rouhani said in phone call with UK PM David Cameroon on 26 March.
Rouhani stressed the talks were an "exceptional opportunity" that helps all national and international interests.
Does war in Yemen affect US-Iran talks?
Iran, the largest Shia country in the Middle East, is the key ally of Yemen’s main Shia rebel group led by Abdul Malek Al-Houthi.
In 2009, then-president Ali Abdullah Saleh accused Iran of funding the rebel group. Later in the same year Houthis and Saudi forces clashed across the border.
"There's too much at stake to let Yemen get in the way of a nuclear deal. The P5+1 never stopped negotiating at the height of the Syrian civil war," Dagres said.
Dagres went on to explain that Yemen would not be a problem in the nuclear negotiations.
The US supported its key ally Saudi Arabia in its strikes on Houthis strongholds in southern Yemen to protect the government led by President Abd-Rabbu Mansour Hadi, according to a White House statement on Thursday.
Saudi Arabia formed a coalition together with nine other Arab countries and launched their first attacks on Houthis last Wednesday, two days before the convening of the annual Arab League summit.
The summit gave the green light to establishing a voluntary joint regional military force to deal with security threats.
On the other hand, Iran harshly condemned the Saudi intervention in Yemen.
Rouhani in his phone call with UK's PM David Cameron said "regional countries should avoid any kind of action which could negatively affect the crisis."
In the meantime, a senior US official told AFP on Thursday that the Saudi strikes would have "no impact" on nuclear talks with Tehran.
"The Iranian government needs to make concessions for the sake of diplomacy," Dagres added.
"The deal is doable," Abbas Arqashi, the Iranian deputy foreign minister, told reporters on Sunday.
"Getting to an accord is doable. Solutions have been found for numerous questions. We are still working on two or three issues... The talks are in their final phase and are very difficult," Arqashi told reporters in Lausanne, AFP reported.
"While negotiations are happening between Iran and the P5+1, it would be unwise for the Iranian government to take any drastic measures during such a sensitive time—they are rational enough to recognise this," Dagres said.