A US cross-party committee to protect the Good Friday Agreement has issued a strongly worded statement criticising the British government's plans to overturn parts of the Northern Ireland Protocol.

The Ad Hoc Committee rejected the purported legal and political justification, saying it had no credibility and undermined the Good Friday Agreement.

The committee is made up of well-known Irish-American politicians and business leaders.

In a statement, it said the bill would "egregiously breach international law" if it was passed and threatened that there would be no US-UK trade deal if the UK damages the agreement.

The bill published this week in the House of Commons will effectively rip up key parts of the deal signed by British Prime Minister Boris Johnson and the EU in 2019.

The EU has launched legal action against the UK in retaliation over the bill.

European Commission vice-president Maroš Šefčovič said the move was illegal.

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The committee added: "The US Congress has for over two decades been resolute in demonstrating its bipartisan commitment to protecting the GFA and has made it abundantly clear that there will be no trade deal with the UK if it continues to put the GFA in harm's way.

"We urge President Biden to use all the diplomatic tools at his disposal to convey to the UK what is at risk and if necessary to suspend discussions on any future trade agreement with the Government of the United Kingdom and its authorized officials until such time as this Bill is rescinded.

"In this instance the United States must not be neutral between our allies in the UK and the European Union.

"The UK Government is acting in bad faith. We agree with Taoiseach Martin that the Bill is "a fundamental breach of trust". It risks the stability of the Good Friday (or Belfast) Agreement of 1998 which has brought peace to Ireland."

"Quite simply, the actions of the Johnson administration demonstrate that it has neither engaged with the EU in good faith, nor exhausted all legal avenues within the Protocol to resolve difficulties, real and imagined. Instead, it seeks to rely on an excuse that avoids its arguments being tested in UK courts. 

"The UK Government purports to justify its conduct as a valid response to alleged violations of the Good Friday Agreement by the Protocol (which it negotiated, signed, and ratified).

"But it cites no specific provision of the Good Friday Agreement which has been allegedly violated. Bizarrely, the same UK Government has consistently instructed its lawyers in litigation against the Protocol to argue that it is fully compliant with the Good Friday Agreement, which it is.

"The Protocol, in short, was negotiated and agreed to protect the Good Friday Agreement; it should not be unilaterally modified in a spurious defense of that Agreement."