Despite Trump’s prior reservations — he told the Wall Street Journal on Jan. 13 that “I don’t love” the plan — there is now broad agreement among senior administration officials that border adjustment is the best approach for a broad overhaul of the U.S. tax code.

The official described the proposal as the “most nationalist” way for the U.S. to tax its companies and said Trump was previously opposed only because he doesn’t like the word “adjustable.” He would prefer to simply call it a border tax, the official said.

Talk of a border tax has contributed to deteriorating relations between the U.S. and Mexico, pushing the countries closer to a trade war that threatens to spoil decades of friendship and economic cooperation. The feud grew increasingly hostile on Friday as Trump said in a Twitter posting that Mexico “has taken advantage of the U.S. for long enough” by not addressing trade deficits and security along the “very weak border.”