US President Donald Trump is planning to add four African countries to the travel ban list, according to media reports.

The four countries are thought to be Nigeria, Tanzania, Sudan and Eritrea, according to multiple US media outlets who reported they had spoken to people who had seen the list.

President Trump, in an interview with Wall Street Journal on the sidelines of the World Economic Forum in Davos, Switzerland, confirmed that he was considering adding some countries to the travel ban list but declined to name them.

The list is not final and could be changed, the Politico website said.

The ban will not be a blanket one for all the listed countries but will be on specific types of visas, such as business or visitor visas.

The list is still being debated but the final announcement could be made next week, media reports said.

In September 2017, President Trump issued a travel ban prohibiting most people from Iran, Libya, Somalia, Syria and Yemen from entering the US.

The ban was challenged in court but a Supreme Court ruling in June 2018 upheld it.