Donald Trump has said he will permanently pause migration to the US from all third world countries.

The US president wrote in a Truth Social post that the decision would allow the US system to fully recover from immigration policies that had eroded the gains and living conditions of many Americans. He did not provide details of his plan or name which countries might be affected.

Trump's comments come a day after an Afghan national was accused of shooting two members of the National Guard in Washington DC, one of whom has died.

This and other announcements after the attack represent a further toughening of Trump's stance towards immigration, which has long been one of his key issues.

Trump previously said Wednesday's shooting in Washington DC underlined a major national security threat and promised to take steps to remove any foreigner from any country who does not belong here.

At the same time, the US suspended processing all immigration requests from Afghans, saying the decision was made pending a review of security and vetting protocols.

Then on Thursday, the US Citizenship and Immigration Services said it would re-examine green cards issued to individuals who immigrated to the US from 19 countries. This list included Afghanistan, Cuba, Haiti, Iran, Somalia, and Venezuela.

Trump's latest post also pledged to end all federal benefits and subsidies to noncitizens and reinforced his view that refugees contribute to social dysfunction in America.

He has labeled the recent shooting incident as an act of terror and reiterated his commitment to maintaining stricter immigration policies from countries considered high-risk.