But the Tanaiste said Ireland was not going to allow a situation where the United Kingdom leaving the European Union without a deal "drags Ireland out of the single market with it".
Chancellor Merkel will have a tete-a-tete will the Taoiseach and a number of meetings during her visit to Dublin. May is expected to try to bring it back for a fourth vote.
Simon Coveney said Ireland had intensified its no-deal contingency planning with the EU Commission but checks at EU ports on Irish products were not a runner.
Mr Varadkar described this as the basis for the Irish economic model.
Mr Juncker told MEPs that April 12 was the "ultimate deadline" for the House of Commons to approve the withdrawal agreement, including the Irish backstop.
Ireland's 500 km (350 mile) border with British-governed Northern Ireland will be the United Kingdom's only European Union land frontier after Brexit, and the question of how to retain seamless trade across it has been a major hurdle in efforts to ensure the UK quits the bloc in an orderly fashion.
"Any extension must have a clear goal and a clear plan", Varadkar said.
"An extension in this context is one thing, but a rolling extension that just leads to further indecision, further majorities against things but for nothing, is not a solution for anyone".
That becomes an even more hard task if Britain leaves the bloc without a deal as Dublin has pledged to maintain the integrity of the European Union's single market, where goods move freely around the bloc without the need for checks.
Discussing his meeting with Mr Macron in Paris on Tuesday, Mr Varadkar said he was "really heartened by the enormous support" that France continued to demonstrate towards Ireland and, by Mr Macron's statement that Ireland would never be abandoned by France or by the EU.
"Chancellor Merkel has a particular interest in the Border".
While the chancellor will not visit the Border area, it is understood people with direct experience will explain how the removal of checkpoints has changed their lives over recent years.
The Taoiseach is getting to the nub of the no-deal border problem.