The Donald Trump administration's hard line on illegal immigrants entering the United States, which involves separating children from their families, has triggered responses ranging from concern to outrage across the political spectrum, with lawmakers under pressure as the President punts the hot potato to Congress.

Republicans from swing states are worried, seeing the party's traditional "family values" brand dented by reports from child detention centres, and an audio recording of wailing children. The crisis may undermine the Republican Party as it heads into a midterm congressional election in five months.