U.S. President Donald Trump doubled down Sunday on his support for a united Ireland, saying it makes sense to merge the Republic of Ireland with the United Kingdom’s Northern Ireland.

Axar.az reports, citing The Associated Press, that Trump made the remarks while attending the Irish Open at his golf course in Doonbeg, western Ireland.

“It just seems to me that you have Northern Ireland and you have Ireland, and it would seem to me that one of the naturals of all time is put them together,” he said.

It’s not that simple.

Trump’s statement Saturday that Irish unification would be “fantastic” touched a live rail in the histories of Britain and Ireland that lies behind a century of division and decades of violence. Reaction, for and against, was swift.

Irish Prime Minister Micheal Martin urged politicians to “keep a calm perspective” on Trump’s comments, and called some of the responses an overreaction.