President Donald Trump was sued over his bid to end automatic citizenship for children born in the US whose parents are unlawfully or temporarily in the country, kicking off a pitched legal fight over his immigration crackdown.

Immigration advocates filed a lawsuit on Monday evening in New Hampshire shortly after Trump signed an executive order to end birthright citizenship. The change, set to take effect in 30 days, would upend more than a century of US policy and court interpretations of the US Constitution.