The Taoiseach says the backstop is off the table in this week's Brexit talks.
Leo Varadkar made the comments ahead of an EU Council summit in Brussels.
The British Prime Minister has travelled to Brussels with the aim of getting more concessions from EU leaders on the backstop.
Theresa May is hopeful those concessions would help pass the withdrawal agreement through her parliament.
Leo Varadkar met Mrs May earlier and said she has some ideas that can work and others that are complete non-runners.
The Taoiseach said "I don't think we could agree to anything that would change the content of the treaty or the withdrawal agreement".
“The backstop is not on the table”. Leo Varadkar very clear heading into negotiations with Theresa May and the EU27 #Brexit pic.twitter.com/xIVtkYDwIz
— Sean Defoe (@SeanDefoe) December 13, 2018