The dollar tumbled to its lowest level in a month after Donald Trump suggested to The Wall Street Journal he favored a weaker dollar, breaking with decades of tradition and intensifying investor concern over the incoming administration’s capacity to surprise.

The president-elect in an interview published Monday described the dollar as “too strong. ” He dismissed a major tax proposal that would favor U.S. exports over imports— known as a border adjustment—that was expected to further boost the dollar, as “too complicated.”

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