Update 10.40pm: Leo Varadkar has said he will raise concerns with President Donald Trump over a possible tit for tat trade war between the EU and US.
Mr Varadkar said tariffs were a road that he did not want either Europe or America to go down.
The Taoiseach made the comments during an interview at the South by South West festival in Austin, Texas.
"As a policy I can't imagine how it would be good for anyone, I don't think it would be good for America, I don't think it would be good for Ireland or the EU," Mr Varadkar said.
A possible trade war has been mooted since Mr Trump announced a 25% import tariff on steel and 10% on aluminium.
The EU has threatened retaliatory tariffs on US goods, including bourbon and jeans.
Mr Varadkar, who began his St Patrick's Day tour of the US on Sunday, said the day before his White House meeting with Mr Trump later this week, the European Commission will announce its response to the tariffs.
"What has been hinted at is tariffs on denim jeans and bourbon whiskey," he said.
"When I hear bourbon whiskey I think the next response might be tariffs against Irish whiskey, so what you get into is a spiral of tit for tats."
Asked what he'll raise in the White House he said: "You can't cover everything but on the very top of that list, or very high on that list will be trade and the risk of a drift in relationships between Europe and America and that really, really scares me."
Update 7.51pm: Taoiseach announces extension of consulate in Texas to boost links with US
Taoiseach Leo Varadkar has announced an extension of his country's consulate in Texas as part of plans to foster more links with a number of key US states.
Mr Varadkar said the move would help his stated aim of doubling Ireland's footprint globally.
The Taoiseach made the comments after a meeting with the Governor of Texas Greg Abbott in Austin on the first day of his St Patrick's Day visit to the US.
"This is a rapidly growing state, growing population, growing economy," Mr Varadkar said.
"We opened a consulate here for the first time in Austin three years ago - as part of my plan to double Ireland's footprint we're going to be expanding that mission."
The meeting was the first in the Taoiseach's week-long trip to the US for the annual St Patrick's Day festivities.
Other scheduled engagements in the Texan city on Sunday included a discussion about Irish innovation at the South By Southwest festival.
Mr Varadkar said there were about 100,000 people working for Irish companies in the US.
The Taoiseach said Ireland would be focusing on creating strong relationships with the states of Texas and California.
The Government's annual St Patrick's Day trip aims to advance Ireland's economic and political interests in the US. It also seeks to celebrate new and old cultural and communities ties between the two countries. This year it will incorporate four cities.
On Monday the Mr Varadkar will meet the Governor of Oklahoma and will also visit a Native American community there.
His meeting with the Choctaw Nation will commemorate the tribe's fundraising efforts for the victims of Ireland's Great Famine in the mid 19th Century.
Mr Varadkar travels to Washington DC on Tuesday where he will deliver a foreign policy address to the Brookings Institution.
That evening, the Taoiseach and Senator George Mitchell will be keynote speakers at a congressional event to mark 20 years since the signing of Northern Ireland's Good Friday Agreement peace agreement.
His Washington engagements also include meetings with senior representatives of Irish companies succeeding in the US market.
On Wednesday, the Taoiseach will address the annual American Ireland Fund gala dinner.
Keeping with recent traditions, the focus of the itinerary will be Mr Varadkar's bilateral meeting with President Trump at the White House on Thursday.
It is likely to include a discussion on the issues faced by the tens of thousands of Irish citizens who live in the US without legal residency.
It will be followed by the annual Speaker's lunch on Capitol Hill and the ceremonial exchange of a shamrock bowl between Mr Trump and the Taoiseach back at the White House.
On Friday, the Taoiseach will be guest of honour at a breakfast hosted by Vice President Mike Pence.
Mr Varadkar will end his trip in New York where his series of engagements will include the St Patrick's Day parade along Fifth Avenue on Saturday.
Earlier: Taoiseach confident Eighth Amendment legislation will be passed by end of year if there is yes vote in referendum
By Elaine Loughlin In Austin, Texas
The Taoiseach is confident legislation to replace the Eighth Amendment will be passed by the end of the year if there is a yes vote in the upcoming referendum.
Speaking in Austin, Texas where he is beginning his St Patrick's Day trip to the US, Leo Varadkar said he had tasked Health Minister Simon Harris with producing legislation which can be pushed through the Oireachtas if the public decides to take abortion out of the Constitution.
Mr Varadkar met with the Governor of Texas Greg Abbott this morning in his first engagement in the US.
However, speaking after their meeting, Mr Varadkar said he had not raised the issue of LGBT rights with the Governor.
Last year, the Republican Governor signed a law that allows adoption or foster care agencies to refuse to place children with certain prospective parents, including same-sex couples if the provider feels it conflicts with their "sincerely held religious beliefs."
Critics said the Bill to protect the religious rights of faith-based groups in state child welfare programs could be used to discriminate against LGBT families in adoptions.
He has also sought to ban transgender people from using the bathrooms of their choice.
During their meeting, Mr Abbott 's introduced the Taoiseach to his wife Cecilia who has Irish ancestry.
Turning to domestic matters, Mr Varadkar said Government had been working on the legislation that would replace the Eighth Amendment and he is confident this legislation could be passed within the lifetime of the Government.
Mr Varadkar said: "If you remember when I was elected as Taoiseach back in June one of the things that I committed to, I gave every minister two or three things to focus on and one of the things that I gave the Minister for Health to focus on was having a referendum this year, ideally by the summer.
"Notwithstanding a few delays along the way, we are actually on track the legislation is now in the Dáil and I am confident that we can have referendum in May and that would allow us to get legislation through within a matter of months.
"We have been working away on that legislation, the policy paper is already done will be able to publish a draft scheme of general scheme of the legislation, we plan to do that by the end of March and if there is a yes vote in the referendum we would then have a couple of months to get that legislation through.
"So I certainly think that can all be done within this calendar year, within the lifetime of this Government," said the Taoiseach.