(Reuters) - Iran has breached a cap on its enriched uranium stockpile set in a 2015 deal with major powers and said it plans to further flout the nuclear agreement, moves which ultimately could lead to the return of all international sanctions on Tehran.

Most U.N. sanctions were removed in January 2016 when the deal was implemented. It is formally called the Joint Comprehensive Plan of Action (JCPOA) and was agreed by the United States, Iran, Britain, China, France, Germany and Russia.

U.S. President Donald Trump withdrew the United States in May 2018 saying the accord did not go far enough and did not address Iran’s missile program or activities in the Middle East.

Iran is arguing that its breach of the enriched uranium cap is not a violation of the accord and is instead a response to the U.S. pullout under the terms of the nuclear deal.

In a July 1 note sent to member states of the International Atomic Energy Agency (IAEA) - and seen by Reuters - Iran said it had officially triggered the nuclear deal’s dispute resolution process on May 10, 2018, after the United States withdrew.

Under that process, if a party is not happy with attempts to address their complaint they can “treat the unresolved issue as grounds to cease performing its commitments in whole or in part.”

However, two Western officials with knowledge of the accord, speaking on condition of anonymity, said Iran has never formally triggered the dispute resolution process.

Iran also argues that it can reduce in its commitment because, under a separate provision, the agreement said: “Iran has stated that it will treat such a re-introduction or re-imposition of the sanctions ... or such an imposition of new nuclear-related sanctions, as grounds to cease performing its commitments under this JCPOA in whole or in part.”

The dispute resolution process could take up to 65 days to play out unless extended by consensus.

The following explains how the process works:

STEP ONE - If any party to the nuclear deal believes another party is not upholding their commitments they can refer the issue to a Joint Commission, whose members are Iran, Russia, China, Germany, France, Britain and the European Union. (The United States was a member before it withdrew from the deal.)

The Joint Commission then would have 15 days to resolve the issue, unless it agrees by consensus to extend the time period.

STEP TWO - If any party believes the matter has not been resolved after that first step, they can refer it to the foreign ministers of the parties to the deal. The ministers would have 15 days to resolve the issue, unless they agree by consensus to extend the time period.

In parallel with - or in lieu of - consideration by foreign ministers, the complaining party or the party accused of non-compliance also could ask for the issue be looked at by a three-member advisory board. The participants to the dispute would each appoint a member and the third member would be independent.

The advisory board must provide a non-binding opinion within 15 days.

STEP THREE - If the issue is not resolved during the initial 30-day process, the Joint Commission has five days to consider any advisory board opinion in a bid to settle the dispute.

STEP FOUR - If the complaining party is not satisfied after this and considers the matter to “constitute significant non-performance,” they could “treat the unresolved issue as grounds to cease performing its commitments under this JCPOA in whole or in part.”

They also could notify the 15-member U.N. Security Council that the issue constitutes “significant non-performance”. In the notification the party must describe the good-faith efforts made to exhaust the Joint Commission dispute resolution process.

UNITED NATIONS SECURITY COUNCIL

STEP FIVE - Once the complaining party notifies the Security Council, the body must vote within 30 days on a resolution to continue Iran’s sanctions relief. A resolution needs nine votes in favor and no vetoes by the United States, Russia, China, Britain or France to pass.

STEP SIX - If such a resolution has not been adopted within 30 days, the sanctions in all previous U.N. resolutions would be re-imposed - referred to as snapback - unless the council decided otherwise. If the previous sanctions are re-imposed they would not apply retroactively to contracts Iran signed.