washington president donald trump keep criticism mexico friday say take advantage u.s. long enough crisis border security trade deepen massive trade deficits little help weak border must change trump write twitter thursday mexican president enrique pena nieto scrap plan trip washington meet trump repeatedly demand mexico pay wall u.s. border halt illegal immigration white house also suggest thursday unite state could impose 20 percent tax goods mexico pay wall send peso tumble speak scrap summit senior trump aide kellyanne conway friday tell fox news relationship implode one meet cancel mutual cancellation separate interview cbs news say tax one fund possibility wave chance mexican retaliation could cost american job tell cbs news want mexico pay wall get awful lot country conway tell cbs white house say tax proposal early stag plan weigh house republicans would exempt export revenues taxation impose 20 percent tax import goods idea know border adjustment tax would significant change current u.s. policy retailers businesses sell import goods keen idea lawmakers express concern impact u.s. consumers cost everything groceries cars office supply would go 20 percent make hard middle class families pay things need every day senate democratic leader chuck schumer say statement trump say mexico take advantage u.s. 'for long enough