Washington DC - The US is freezing all asylum decisions, officials said Friday, as President Donald Trump hardens his anti-migrant stance after an Afghan national allegedly shot two National Guard members this week in Washington.

Wednesday's attack on the soldiers – one of whom died from her injuries – has ignited a fresh crackdown on foreigners in the US, with Trump also pledging to suspend migration from "third world countries."

Joseph Edlow, director of the US Citizenship and Immigration Services (USCIS), said his agency has "halted all asylum decisions until we can ensure that every alien is vetted and screened to the maximum degree possible."

That followed Trump's announcement late Thursday of plans to "permanently pause migration from all Third World Countries to allow the US system to fully recover."

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Asked which nationalities would be affected, the Department of Homeland Security pointed AFP to a list of 19 countries – including Afghanistan, Cuba, Haiti, Iran, and Myanmar – already facing US travel restrictions since June.

Meanwhile, Secretary of State Marco Rubio said Friday that the US had temporarily stopped issuing visas to all individuals traveling on Afghan passports.

"The United States has no higher priority than protecting our nation and our people," he said.