The Taoiseach said: "I think it is likely that the United Kingdom parliament sooner or later will agree to what has been agreed by the 28 member state governments".
What has the Prime Minister said before?
Here is a look at the U.S. president's comments and the background to the mooted transatlantic post-Brexit trade deal.
If Britain leaves the European Union in March with no deal, but with some agreements to avoid major disruption to trade and travel, the economy will be 5.5 percent smaller by 2030 than under continued European Union membership.
"We have a working group set up and that is working very well, has met several times and is continuing to work with the USA on this". "We've met with the president on a number of occasions in recent months".
The timing gives Mrs May a fortnight to avert what threatens to be a humiliating defeat at the hands of scores of Conservative rebels.
She will now embark on an intensive nationwide campaign promoting the plan - and the dangers of no-deal - ahead of the vote by lawmakers on or around December 12, according to reports.
"The message I have clearly heard here today from across the board - from the voluntary sector, from young people, from businesses, from the cultural sector, from academics - is the importance of that certainty and the importance of Parliament accepting that deal so we can move on to develop our future", she said.
Former defence secretary Sir Michael Fallon confirmed he will not vote in favour of the agreement when it comes to Parliament, where he said it seems "doomed" to fail.
Plaid Cymru, the SNP, the Liberal Democrats and the Green Party had said that if a debate took place, they should be included.
"This is that deal".
"We will always stand by you, we are proud that Gibraltar is British", May added.
However, with around 90 Conservative MPs pledged to vote down the deal, the prime minister faces a major struggle to win the vote.
Mr Trump also told reporters outside the White House that the deal sounds like it will be good for the European Union.
A very turbulent period now lies before the members of Britain's parliament, as they will vote on the deal in the coming weeks.
"No one knows what would happen if this deal didn't pass", May told the House of Commons. "It would open the door to more division and more uncertainty, with all the risks that will entail".
"There are lawmakers, for example on the opposition Labour side, who say that the deal goes too far. It's an act of national self-harm", he said.
"This botched deal is still a bad deal for the country and all yesterday did was mark the end of this Government's failed and miserable negotiations".
The independent National Institute of Economic and Social Research found that trade with the European Union - especially in services - was likely to be more costly after Brexit and have an adverse effect on living standards.
The prime minister vowed to warn her rebellious MPs that at least half could lose their seats at the next election if they fail to deliver her Brexit deal, the source said.
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