Foreigners seeking to adjust their immigration status in the United States to secure green cards will ​have to do so from outside the country via ‌the State Department, the U.S. Citizenship and Immigration Services (USCIS) said on Friday, in a move criticised by aid groups.

USCIS announced the move in a ​policy memo, which directed officers to consider relevant factors and ​information on a case-by-case basis when determining whether extraordinary ⁠relief is warranted.

"An alien who is in the U.S. temporarily ​and wants a Green Card must return to their home country ​to apply," said the U.S. Department of Homeland Security, which has oversight of USCIS.

"This policy allows our immigration system to function as the law intended ​instead of incentivising loopholes."

The USCIS said the new policy will ​free up agency resources to focus on processing other cases.

HIAS, an aid group ‌that ⁠provides services to refugees, among other groups of immigrants, said USCIS was forcing survivors of trafficking and abused and neglected children to return to the dangerous countries they fled in order to ​process their applications ​for green cards ⁠, granting them permanent residency in the U.S.

Friday's policy change is the latest in a series of steps taken by U.S. President Donald Trump over the last year ⁠to tighten U.S. immigration.

Last year, the Trump administration moved to shorten the duration of visas for students, cultural exchange visitors and ⁠members ​of the media.

In January, the State Department ​announced that it had revoked more than 100,000 visas since Trump took office the ​year before.