Encouraged by a sharp downturn in illegal border crossers, the US administration is ramping up a crackdown on undocumented immigrants, taking aim at both Central American labourers and Indian tech workers in Silicon Valley.

Police, prosecutors and judges have been ordered to take a harder line against all illegal immigrants, detaining anyone without papers and vigorously prosecuting more of them.

Hiring standards for immigration agents are being eased to quickly beef up their ranks, more facilities to hold detained immigrants are being built, and more judges are being added to handle cases.