France, the UK, and Germany officially notified the UN Security Council on Thursday that the "snapback" mechanism against Iran has been activated.
Since the announcement, a 30-day period will take effect during which the mechanism can be halted. If it is not stopped, all sanctions imposed on Iran in 2015 will be reinstated.
European nations are demanding that Iran resume negotiations for a new nuclear agreement and grant access to all nuclear sites, including uranium stockpiles damaged during the war with Israel.
Deputy foreign ministers from the three countries met with Iran's deputy foreign minister on Tuesday.
The meeting yielded no significant progress, a source familiar with the matter told The Jerusalem Post.
"The Iranians make promises and declarations but fail to deliver anything substantial that could delay the snapback process," the source said.
Iran's Foreign Ministry stated after the meeting: "Iran remains committed to diplomacy and a mutually beneficial diplomatic solution. It is high time for the E3 and the UN Security Council to make the right choice and give diplomacy time and space."
According to a source familiar with the matter, the foreign ministers of Germany, France, and the UK, along with the EU's Foreign Affairs Chief, Kaja Kallas, held discussions with US Secretary of State Marco Rubio.
German Foreign Minister Johann Wadephul on Thursday said the reimposition of UN sanctions on Iran could mark the beginning of a new phase in diplomatic negotiations.
His made the remarks after a decision by Britain, France and Germany to initiate a 30-day process to reimpose the sanctions over Iran's nuclear program.
Wadephul called for Iran's full cooperation with the International Atomic Energy Agency and a clear commitment to direct negotiations with the United States.
US Secretary of State Marco Rubio welcomed the initiative, adding that France, Britain, and Germany had laid out a clear case of Tehran's “significant non-performance" of its nuclear commitments.
Rubio said in the statement that the United States remains available for direct engagement with Iran "in furtherance of a peaceful, enduring resolution to the Iran nuclear issue."
'Illegal and regrettable'
A senior Iranian official decried the sanctions as "illegal and regrettable," to Reuters, adding that Tehran was reviewing its options, including withdrawing from the Non-Proliferation Treaty.
"The move is an action against diplomacy, not a chance for it ... However, Iran will continue diplomacy with the E3 ... (But) Iran will not concede under pressure," added the senior official.
Inspecting Iran's nuclear facilities
This week, a first group of inspectors from the International Atomic Energy Agency (IAEA) arrived in Iran.
Iran's news agency reported that the inspectors visited the civilian nuclear reactor in Bushehr. A source familiar with the matter told the Post that Iran is currently refusing access to sites damaged in the conflict with Israel.
As a first step, if an agreement is reached between the IAEA and Iran, inspectors will be allowed to visit undamaged nuclear sites.
"Progress has been made on oversight discussions. Some issues remain unresolved and are still under discussion. Inspections are expected to resume at the agreed-upon sites," a source familiar with the negotiations told the Post.