(Bloomberg) -- The European Union will need at least several months to sign off on the landmark post-Brexit deal to smooth cross border trade in Northern Ireland as officials are still assessing the legal steps needed to implement the more than 300-page agreement.

European Commission President Ursula von der Leyen and UK Prime Minister Rishi Sunak agreed on a set of changes to the Northern Ireland Protocol that include three legislatives proposals on medicines, customs and agricultural controls, each of which needs to be approved by the European Parliament and the bloc’s 27 member states. The compromise also includes several targeted amendments to the protocol itself. 

The process could be completed realistically by the end of the year and may be finalized even sooner, according to people familiar with the matter.

One of the targeted amendments would add a mechanism, known as the Stormont brake, to allow Northern Ireland, as a last resort, to opt out of amendments or revisions to existing EU laws. 

The brake, which Sunak called a “veto,” could allow old versions of EU rules to remain valid in Northern Ireland, while amended laws would apply in the EU. Some member states have raised questions about the consequences of this change for the level playing field in the EU’s internal market, the people said on condition of anonymity. 

The deal is aimed at putting to rest the thorniest dispute between the UK and the EU since London left the bloc, and both sides hope it could lead to a renewed partnership. 

The original Brexit treaty gave Northern Ireland unique access to both the UK and EU markets, but effectively imposed a customs border in the Irish Sea between Great Britain and the region. That proved tough to implement and controversial in the challenging politics of the area. It also became a tempting target for pro-Brexit politicians eager to prolong the battle with Brussels.

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EU member states agreed during a discussion Monday that the proposed deal doesn’t amount to a substantial change to the protocol, but they requested more information about the process ahead, an EU diplomat said.

The bloc’s executive arm, the European Council’s legal service and Sweden, which currently holds the bloc’s rotating presidency, are expected to outline a tentative timeline in the coming days. A working group on the UK issue is set to meet Friday to conduct the first substantial discussion on the deal, added the diplomat, who spoke on condition of anonymity because the discussions are private.

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Member states are expected to adopt in March the proposed amendments to the protocol before they are confirmed by an EU-UK joint committee later that month. The legislative changes would take a few additional months to win final approval. 

The new deal still needs to be put into international and domestic law. Some new arrangements, like taxation, would apply immediately, but others will need to be phased in over the next couple of years. The UK government expects some new arrangements for goods, food products, pets and plant movements to be introduced later this year and into 2024.

--With assistance from Ellen Milligan.

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