Former president Mary Robinson has called on the Taoiseach to urge the US to end its military and financial support for Israel during his meeting with Joe Biden at the White House.
The chairwoman of the Elders group said the focus should not be on the humanitarian situation in Gaza, but on political responses to it.
Speaking on RTÉ's News at One, Mrs Robinson said: "Yes the humanitarian situation is utterly catastrophic and dire, reducing a people to famine, undermining all our values, but the message I want to deliver on behalf of the Elders is a direct message to our Taoiseach Leo Varadkar."
She said that Mr Varadkar should not spend "too much time" during his meeting with Mr Biden on the humanitarian situation and instead deliver a "direct" political message.
"The United States can influence Israel by not continuing to provide arms, it has provided a lot of the arms, bombs that have been used on the Palestinian people and he's continuing to do that and he's also providing money.
"This government of Prime Minister Netanyahu is on the wrong side of history, completely, is making the United States complicit in reducing a people to famine - making the world complicit.
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"Leo Varadkar has access today to President Biden. He must use this completely politically at all levels with the speaker of the House with everyone, to make it clear that Israel depends on the United States for military aid and for money, that's what will change everything."
'Stop the arms supply, stop the money'
Mrs Robinson said: "I want the political message from the Taoiseach and from Irish representatives to be very clear".
She said such a message would call for an "indefinite ceasefire and also to encourage more thinking about the way forward which means the two-state solution.
"This I think cannot happen under Prime Minister Netanyahu he seems very opposed to the idea".
Mrs Robinson said the Taoiseach has access to Mr Biden to urge him to "stop the arms supply" and "stop the money".
"So, that Israel wakes up to its realities and hopefully goes on the right track," she said.
"I feel that if this direct political step is taken by Biden that they’re not going to provide anymore military support, they're not going to provide anymore budgetary support at the moment for Israel until this government changes course or there’s a new government to change course that I think will help concentrate on a ceasefire."
The Oval Office meeting took place at a time of heightened political tension over Israel's war in Gaza - tension between the US and Israeli governments spilling into the open yesterday in remarks by Senate majority leader Chuck Schumer, who called for Israel to hold elections to get rid of the Netanyahu government.
Speaking at an event hosted at the Irish Ambassador's residence in Washington last night, Mr Varadkar said the relationship between Ireland and the US could not be stronger.
"A hundred years of official diplomatic relations have woven a relationship that is stronger and deeper than ever," Mr Varadkar said at an event hosted at the Irish ambassador's residence in Washington DC last night.
In his remarks, he also celebrated the long-standing, two-way trade relations between the two countries, emphasising that he was "proud" Ireland was one of the top ten investors in the US.
On Sunday, the Taoiseach will also gift Mr Biden a bowl of shamrock as part of an annual tradition to mark St Patrick's Day.
The Taoiseach will also today attend the traditional speakers lunch on Capitol Hill, where he will press new Speaker of the House Mike Johnston to allow a vote on a $60 billion military aid package for Ukraine.
The Speaker is viewed as the main stumbling block to freeing up billions of dollars in munitions for front line troops, but indicated yesterday he may move to allow a free vote on the funds.
Mr Varadkar started the trip on Monday, and since then has spoken several times at about how he will use the special platform of the St Patrick's Day visit to press Mr Biden to back a ceasefire in the Gaza, while also thanking the US for leadership in support for Ukraine.
He said that the highlight of his trip so far was seeing Northern Ireland First Minister Michelle O'Neill and Deputy First Minister Emma Little-Pengelly jointly address the Ireland Funds gala in Boston.
Additional reporting Sean Whelan
