The Trump administration has said it will re-examine green cards issued to individuals who immigrated to the US from 19 countries.
The head of the US Citizenship and Immigration Services, Joseph Edlow, said the president had directed him to conduct "a full scale, rigorous re-examination of every green card for every alien from every country of concern".
When asked by the BBC which countries were on the list, the agency pointed to a June proclamation by the White House that included Afghanistan, Cuba, Haiti, Iran, Somalia and Venezuela.
The announcement comes in the wake of an Afghan national allegedly shooting two National Guard troops in Washington DC on Wednesday, gravely injuring them both.
The suspect, Rahmanullah Lakanwal, came to the US in 2021 under a programme that offered special immigration protections to Afghans in the wake of America's withdrawal from Afghanistan.
US President Donald Trump said the shooting underlined a major national security threat.
Edlow's social media post on Thursday about the sweeping green card review did not explictly mention that attack.
"The protection of this country and of the American people remains paramount, and the American people will not bear the cost of the prior administration's reckless resettlement policies," he said.
There were no further details about what the re-examination would look like.
The June proclamation his agency highlighted to the BBC set out an aim to restrict foreign nationals from entering the US to protect from "foreign terrorists and other national security and public safety threats".
The administration said security concerns and the overstay rate of business, student and tourists visas were among the reasons for a country to make the list.
Other countries whose green card holders will undergo this examination include Myanmar, Chad, the Republic of Congo and Libya.
