Iran wants all US sanctions to be lifted at nuclear talks that resumed Monday so that the Middle Eastern country can continue to export crude oil, Iran's foreign minister said.

Diplomats from the US, UK, France and Germany have become pessimistic about the talks as Israel warned that Iran was preparing to enrich uranium to military-grade levels.

"If we work hard in the days and weeks ahead, we should have a positive result," Enrique Mora, the EU diplomat who is chairing the talks, said after the opening day.

But "it's going to be very hard -- difficult political decisions have to be taken," he added.

Mora however disputed comments from Iran and China seeming to suggest that the talks' focus would be on lifting sanctions against Iran, rather than on Tehran observing the terms of the nuclear deal. He said that both aspects needed to be discussed simultaneously.

What did Iran say?

Iran returned the negotiating table in Vienna at 6 p.m. local time, with global negotiators hoping to reinstate the Joint Comprehensive Plan of Action (JCPOA), which the US abandoned in 2018 under President Donald Trump.

Iran said it was ready to return to the terms of the arrangement if US sanctions were dropped.

"The most important issue for us is to reach a point where, firstly, Iranian oil can be sold easily and without hindrance," Foreign Minister Hossein Amirabdollahian was quoted as saying by state media. "The money from the oil is to be deposited as foreign currency in Iranian banks — so we can enjoy all the economic benefits stipulated in [the] Joint Comprehensive Plan of Action."

Assessments of Iran's lucrative oil industry show that the Middle Eastern country has seen its exports drop from 2.8 million barrels per day (bpd) in 2018 to as low as 200,000 bpd.

Sanctions on Iranian oil sales were reimposed by the US after it withdrew from the JCPOA.

Separately, on Monday Iranian Foreign Ministry spokesman Saeed Khatibzadeh said it was "intolerable" for the West to grant anything other than the terms of the JCPOA agreed in 2015.

What are the complexities of the talks?

The nuclear negotiations, now in their eighth round, were suspended for five months after hardline Ebrahim Raisi became president in Iran earlier in 2021.

Israel voiced some of the strongest concerns about Iran's enrichment of uranium, which increased after the US pulled out of the JCPOA and imposed harsh sanctions in 2018.

Though Iran insists that its nuclear program is peaceful, Israel warned in November that the Islamic Republic had taken steps to enrich uranium to the 90% required for weapons.

But, on Monday, Israeli Foreign Minister Yair Lapid said: "Israel is not opposed to any deal."

"We oppose a deal that does not enable true oversight over the Iranian nuclear program, nor over the Iranian money, nor over the Iranian terror network," Lapid told the Israeli parliament's Foreign Affairs and Defense Committee in Jerusalem.

Diplomats from the remaining parties to the deal -- China, Britain, France, Germany and Russia -- are in talks in Vienna with Iran and the US, with the two sides refusing direct contact.

Though the Russian ambassador to the UN in Vienna Mikail Ulyanov tweeted that the Iranian statement was "a positive message," EU and US negotiators recently expressed frustration at the lack of progress.

Their message was echoed by the chairman of the talks, who explained that this was the reason for holding the negotiations between Christmas and New Year's Eve.

"There is a sense of urgency in all delegations that this negotiation has to be finished in a relatively reasonable period of time. Again, I wouldn't put limits but we are talking about weeks, not about months," Mora said.

Last week the US said negotiations could wind down in a few weeks, with European diplomats warning that they are "rapidly reaching the end of the road."

jc/msh (Reuters, AFP, AP)