candidacy for president mr. trump singled out mexican immigrants. >> they're bringing drugs. they're bringing crime. they're rapists. and some, i assume, are good people. >> reporter: with the exception of one year, illegal border crossings into the u.s. reached a 40-year low in 2015 according to homeland security, but drug-related violence in central america has triggered a surge of undocumented migrants. >> who is going to pay for the wall? >> mexico! >> reporter: while mr. trump has long said that mexico will finance the wall, its government has balked. the white house proposal does not include a cost estimate, and it will be up to congress to fund the project. today the president told abc news that u.s. taxpayers may have to front the money. >> all it is is we'll be reimbursed at a later date from whatever transaction we make from mexico. >> reporter: scott, mexico is america's third largest trading partner, and today mexican officials came to the white house for their first meeting