India, May 23 -- The US has sharply curtailed a key immigration route used by hundreds of thousands of Indian professionals, directing officers to approve green card applications filed from inside the country only in "extraordinary circumstances" - the latest in a series of curbs that have, according to new data, driven down H-1B visa registrations for people from all nations.

The drop in registrations is 38.5%, a reflection of the Trump administration's tough-on-immigrants policy that has reshaped the prospects of Indian workers who make up 71% of all approved H-1B applications.

The US Citizenship and Immigration Services (USCIS) announced the policy change on Thursday through a new memo, instructing officers to default to consular pro...