The United Kingdom’s ambassador to the United Nations said on Monday that London and other European parties are prepared to reinstate sanctions on Iran should it continue to advance its nuclear programme.

“Given Iran’s dangerous advances which have brought it to the brink of being able to develop a weapon, this situation should be of grave concern for this council,” Ambassador Barbara Woodward told a UN Security Council meeting focusing on implementation of the 2015 Joint Comprehensive Plan of Action (JCPOA), commonly known as the Iran nuclear deal.

The JCPOA, given the force of international law by a Security Council resolution, included what’s known as a “snap back” mechanism, whereby any signatory to the accord can claim Iran is in violation of its terms, almost inevitably leading to the restoration of the sanctions in place before the pact’s signing.

The effect of those snap-back measures, though, have faded over time as Tehran has pocketed hundreds of billions of dollars due to the expiry of several critical sanctions.

While the JCPOA as a whole will sunset in October 2025, Woodward said on Monday that “we will continue to keep all diplomatic options on the table, including triggering U.N. snap back before October 2025, if necessary.”

The Trump administration pulled out of the JCPOA in 2018, and since then Iran has violated a number of its terms, daring international organisations to take action. According to the latest report from the International Atomic Energy Agency, Iran holds 30 times the stockpile of uranium allowed under the nuclear accord, and has enriched it to near-weapons-grade levels.

Iran has also revoked the accreditation of IAEA inspectors and disconnected monitoring systems in its nuclear facilities. Additionally, it has refused to give credible answers to questions about trace particles of uranium found at undeclared nuclear sites.

Robert Wood, deputy US ambassador to the United Nations, said during Monday’s session that “The United States is prepared to use all means necessary to prevent a nuclear-armed Iran,” adding that “Iran’s actions suggest it is not interested in verifiably demonstrating that its nuclear program is exclusively peaceful.”

It was reported last week that Tehran is set to triple or possible quadruple its uranium enrichment capacity at Fordow, one of the country’s most secretive nuclear facilities, where it is installing some 1,400 advanced IR-6 centrifuges. Under the terms of the JCPOA, Iran had committed not to install or operate those centrifuges, and not to use Fordow for enrichment purposes.

Tehran’s decision to do so is potentially an answer to a censure of the Islamic Republic on June 5 by the IAEA board of governors, which demanded it comply with the IAEA and reinstate inspections. The effort was led by the so-called E3 of the United Kingdom, Germany and France.