While people from those countries will still be able to visit the US as tourists, citizens from Nigeria, Eritrea, Sudan, Tanzania, Kyrgyzstan and Myanmar will now be blocked from obtaining certain types of visas.
Immigration officials say the new measures were the result of failures by the six countries to meet US security and information-sharing standards.
"These countries, for the most part, want to be helpful but for a variety of different reasons simply failed to meet those minimum requirements that we laid out," acting Homeland Security Secretary Chad Wolf told reporters on Friday.
He said officials would work with the countries on bolstering their security requirements to help them get off the list.
US President Donald Trump first introduced a travel ban in 2017. It currently closes US borders to citizens from seven countries, most of them with Muslim majorities.
In 2018 the US issued more than 8,000 immigration visas to citizens of Nigeria. That’s twice as many immigration visas than to the other five nations combined. Just over 2,000 were issued to Sudanese nationals, 290 to Tanzanians, and just 31 to Eritreans.
The US had previously announced a ban on certain types of visas for Eritreans in 2017. This would suspend the issuance of visas that can lead to permanent residency for nationals of Nigeria, Eritrea, Kyrgyzstan, and Myanmar.
Sudanese and Tanzanian nationals will no longer be allowed to apply for "diversity visas", which are available by lottery for applicants from countries with low rates of immigration to the US.
Mr Wolf said non-immigrant visas given to people for temporary stays - including visitors, those doing business or people seeking medical treatment - would not be impacted by the new rules.
Of the new nationalities facing visa restrictions, Nigerians account for the most immigration to the US. Kyrgyzstan and Sudan have large Muslim majorities, while around 50% of people in Nigeria and Eritrea are Muslim. Tanzania also has a sizable Muslim community.
In January 2017, Trump signed the controversial travel ban initially excluding citizens from seven Muslim majority countries. This was however modified after a series of court challenges. The ban now affects citizens from Iran, Lybia, Somalia, Syria, Yemen, Venezuela and North Korea.
In the meantime, the Trump administration on Thursday announced it was imposing visa restrictions on Ghana, blaming the African country for not accepting its own citizens ordered to be removed from the United States, Reuters reports.
According to a statement from the Department of Homeland Security, U.S. Secretary of State Mike Pompeo “has ordered consular officers in Ghana to implement visa restrictions on certain categories of visa applicants…
Without an appropriate response from Ghana, the scope of these sanctions may be expanded to a wider population.”
DHS Secretary Kirstjen Nielsen said: “Ghana has failed to live up to its obligations under international law to accept the return of its nationals ordered removed from the United States…We hope the Ghanaian government will work with us to reconcile these deficiencies quickly.”
- Countries: Caribbean