Washington (CNN) The White House is shifting its goal post again over President Donald Trump's threat last week to close the southern border.

Now, instead of blaming Mexico for an increase in undocumented migration and threatening to close the border within a week if the country didn't increase apprehensions, the White House is blaming Congress for lenient immigration laws and is dangling the potential border closure on no specific deadline.

The shift in tone comes ahead of the President's Friday visit to the US-Mexico border, which Trump has been teeing up to the press over the last two weeks.

In Trump's initial threat last week, he called on Mexico to apprehend more migrants moving northward from Central America, eventually attempting to enter the US illegally.

"Mexico must use its very strong immigration laws to stop the many thousands of people trying to get into the USA," or else the "next step is to close the border," Trump said at the time, giving Mexico until the following week to increase apprehensions.

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