The Northern Ireland Secretary of State Brandon Lewis and the UK's Brexit minister David Frost have warned of possible disruption to peace in Northern Ireland if changes are not made to the Northern Ireland Protocol.

In a joint article in The Irish Times, they say this week's extension of a grace period in the row over the shipment of some goods from Britain to Northern Ireland was "welcome" but that the extension "addresses only a small part of the underlying problem".

They have warned the European Union that the protocol - negotiated as part of the Brexit withdrawal deal - risks "damage" to the Good Friday Agreement unless a "new balance" is found in terms of customs checks.

It comes after German Chancellor Angela Merkel, after holding talks with British Prime Minister Boris Johnson at his official country residence yesterday, expressed optimism that "pragmatic solutions" can be reached on the protocol.

Following a request from the UK, the EU on Wednesday agreed to continue to allow chilled meats to be shipped to Northern Ireland from Britain for another three months.

The deal avoids a trade dispute by delaying the ban until 30 September while efforts continue to find a lasting solution.

Speaking in Cork this afternoon, Taoiseach Micheál Martin said "there is a way" for sustainable solution, which he said was within the Withdrawal Agreement that the UK government signed up to.

He said the UK government should acknowledge the approach of the EU in terms of the extended grace period.

Mr Martin added that EU leaders have dealt in good faith, and that it was time for Britain to "reciprocate that generosity of spirit that EU leaders have shown".

With a reprieve in place, Mr Frost and Mr Lewis urged Brussels to adopt a softer approach to the implementation of the protocol - a treaty Mr Frost helped to negotiate - or else risk further economic disruption and possibly even upsetting the peace in Northern Ireland.

The potential prohibition on chilled meats from Britain is one result of Brexit's contentious protocol, which has created a series of economic barriers on Irish Sea trade.

The protocol is aimed at avoiding a hard border on the island of Ireland by effectively keeping Northern Ireland in the EU's single market for goods.

But Unionists, who have protested against the protocol in recent months, have complained the terms are splitting Northern Ireland from Britain and hitting the pockets of businesses, with suppliers either giving up exporting across the Irish Sea or facing added checks and costs to do so.

In their newspaper article, the two British ministers said: "Opposition is growing, including among many people who are not normally active in political life. That is not a stable basis for the future.

"The current process to resolve all these difficulties is not working and risks creating a series of rolling crises as we lurch from one deadline to another.

"Wednesday's agreement to extend by three months the right to circulate British sausages and chilled meats in Northern Ireland is welcome, but addresses only a small part of the underlying problem.

"In short, a seriously unbalanced situation is developing in the way the protocol is operating - this risks economic harm in Northern Ireland and damage, in turn, to the essential balance within the Belfast Agreement itself."

Mr Lewis and Mr Frost called for a "new balance in the way the protocol is operated" to be put into place "rapidly" and questioned how the EU's insistence on stricter application of the protocol would help matters.

They asked: "If operating the protocol on the current basis is making the situation worse, then how can pressing for an even more rigorous assertion of it make sense?"

The pair said that the UK would have to "consider all our options" if no solution is forthcoming as ministers have "an overriding responsibility and obligation to support peace" in Northern Ireland, in what will likely be read as a further threat to act unilaterally to suspend irksome elements of the protocol.

Mr Johnson, at a joint press conference with Mr Merkel, said he hoped the "wurst is behind us" when it came to the chilled meat saga.

The British Ambassador to Ireland has said that the way the protocol is being implemented is not delivering for all communities in Northern Ireland.

Speaking on RTÉ Radio One, Paul Johnston said: "The Northern Ireland Protocol was first and foremost for us about protecting the Good Friday Agreement, while also of course protecting the EU single market, but what that means in practice is that people in Northern Ireland who identify as British should be able to still feel practically and economically connected to the rest of the UK."

Mr Johnston said that while the protocol provides that both sides should be "making the best endeavours to achieve that", he said the way it was being implemented is not delivering that.

"That's why we see big disaffection with the protocol among the unionist community in Northern Ireland and significant problems for business in Northern Ireland.

"That is in no one’s interest so we want to find sustainable solutions within the framework of the protocol that rebuilds cross community support for it."