Reuters/Henry Romero
Spicer said border tax would be part of a broader tax reform package, according to the report.
The announcement comes the same day that Mexican president Enrique Pena Nieto canceled a trip to the US over Trump's proposal to build a wall along the length of the US-Mexico border.
Trump has long said that Mexico will pay for the cost of building the wall, which Republicans have estimated as $12 million to $15 million. Nieto has said Mexico will not pay for the wall.
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