Northern Ireland First Minister Michelle O'Neill has said she could not live with a decision to travel to Washington DC while the US administration was "threatening to annex and steal" the land of the Palestinian people.
She said she could not be part of a Shamrock reception in the White House because of the "very dangerous, very threatening rhetoric" from President Donald Trump.
The comments came as Sinn Féin announced that the party would not travel to the US as part of "a principled stance against the threat of mass expulsion of the Palestinian people from Gaza".
Stormont's First Minister rejected suggestions that the decision contradicts her repeated pledge to be a 'First Minister for all'.
She told the PA news agency that she believes the party has made the right decision.
"I am a First Minister for everybody, and I've borne that out every day in my role in the last year since I took up that post," Ms O'Neill said.
"But there are times when political leaders are tasked to make a decision, and I had to make a decision, and I believe that the right decision at this time is to come down on the side of humanity.
"I couldn't in good conscience travel to the United States, be part of a Shamrock reception in the White House, at a time where the new US administration is actually actively threatening to remove Palestinian people from their land, to seize their land, and they've very much moved away from a two-state solution.
"I couldn't in all conscience make that trip at this time. I just think that there are times whenever we'll all reflect, and certainly whenever my grandchildren ask me, what did I do whenever the Palestinian people were suffering, I could say that I stood on the side of humanity."
Ms O'Neill said the party will continue to engage with the US administration on economic matters, saying she will travel to North Carolina as part of a economic mission about job creation.
Earlier this month, US President Donald Trump suggested Israel would turn Gaza over to the US for redevelopment into the "Riviera of the Middle East" - involving a mass displacement of Palestinians from the territory.
The proposals were widely condemned and later comments from the US administration sought to suggest the displacement would be voluntary and temporary.
Speaking today, Sinn Féin leader Mary Lou McDonald said: "I've followed with growing concern what's happening on the ground in Gaza and the West Bank and, like many other Irish people, have listened in horror to calls from the president of the United States for the mass expulsion of the Palestinian people from their homes and the permanent seizure of Palestinian lands."
She added: "I've made the decision not to attend the event in the White House this year as a principled stance against the call for the mass expulsion of the Palestinian people from Gaza, something which I believe demands serious dissent and objection."
The Sinn Féin move follows a similar announcement by the SDLP in recent weeks, and echoes calls from a number of other Dáil Opposition parties.
A senior Government representative said the boycott will not "help anybody in Palestine" while the DUP branded the boycott as "reckless".
Taoiseach Micheál Martin has yet to receive a formal invitation to a bilateral meeting with Mr Trump at the White House, but the Taoiseach has said he expects the meeting to go ahead.
McDonald says Taoiseach should travel to White House
Speaking on RTÉ's Six One News, Ms McDonald said her party made the "principled decision after a lot of thought".
She said the White House events were essentially a bilateral between the Taoiseach of the day and the US President.
"The Taoiseach uniquely has an opportunity and a reasonability in his exchanges with the President to bring the Irish view in respect of Palestine, observance of international law and to directly push back against this threat that has been made against the Palestinian people."
She insisted that Sinn Féin was not making any call for the Taoiseach not to attend a bilateral meeting with Mr Trump, instead saying it was important that he uses the opportunity to speak for the people of Ireland and reflect their support for Palestinians.
Ms McDonald said if she were Taoiseach, she would be going to the White House.
"I think whoever is in the role of Taoiseach has uniquely that opportunity to have that access to the American President, that opportunity for an exchange and not alone that, multiple platforms throughout the events to set out very clearly the Irish position and the Irish view."
She said it would be "unforgivable" if Mr Martin did not ask the US president to withdraw his remarks about Gaza.
Ms McDonald added: "I would ask him to reflect the true spirit of Irish people at home and abroad, for justice, for fairness, for freedom, and to articulate that in the clearest possible terms."
Taoiseach accuses Sinn Féin of 'engaging in politics'
Mr Martin, meanwhile, accused Sinn Féin of "engaging in politics" over its boycott.
He said there was a need to continue engagement with the US administration to protect jobs in Ireland as well as trade between the two countries, adding: "It is very important because, first of all, the economic relationship between Europe and the US and between Ireland and the US is an extremely important one, very robust one."
The Taoiseach said it was also important to keep engagement with the US to offer Ireland's perspective on the conflicts in Ukraine and the Middle East.
Mr Martin said: "We need a consolidation of the ceasefire, we need a massive surge of humanitarian aid into Gaza, and we need to create a political pathway to a two-state solution."
Ms McDonald rejected assertions that her party's stance would undermine Ireland's efforts to protect its economic interests in the face of potential new US tariff and tax policies.
She said the party was aware that "Irish jobs and Irish interests need to be protected" but added that Irish political leaders need to state "firm opposition" to the policy of the US administration.
Sinn Féin was also challenged on how it believed it was right for the Taoiseach, as Ireland's head of government, to go to the White House while Ms O'Neill, as joint leader of Northern Ireland's devolved government, should boycott the St Patrick's Day events.
Sinn Féin said it highlighted that the Taoiseach's engagement with Mr Trump was "distinct" and "unique", as he would have a bilateral political meeting with the president - something the Stormont First Minister would not have.
"The Taoiseach is uniquely placed in this scenario," said Ms O'Neill.
"He will have an opportunity to sit down with the president of the United States and to make his views known.
"So I think that it is right, as Mary Lou has said, it is absolutely right that the Taoiseach goes and he doesn't miss that opportunity."
However, DUP leader Gavin Robinson said the decision "speaks volumes" about where Northern Ireland sits on Sinn Féin's list of priorities.
Mr Robinson questioned how Ms O'Neill's decision to stay away from the US capital matched with her oft-repeated pledge to be a "First Minister for all".
He said the DUP would be represented in Washington DC in March.
Mr Robinson added: "The United States is a key economic partner for Northern Ireland.
"Turning away from that relationship, particularly at a time when we need continued international support, is a reckless move that does nothing to advance the interests of people and businesses in Northern Ireland."
