Why is the ban being put in place?
The move is aimed at reducing the number of undocumented immigrants, the Trump administration says.
He is expected to sign executive orders in coming days that include a temporary ban on most people from conflict-hit countries who are seeking refuge in the US.
A suspension of visas for citizens of seven Muslim countries could also be put into place.
Trump tweeted that a “big day” was planned on national security on Wednesday.
Which countries could face visa restrictions?
Syria, Iraq, Iran, Libya, Somalia, Sudan and Yemen are reportedly the countries that have been marked for visa rejections.
The exact number of refugees and immigrants from these countries already residing in the US is not available.
However, Arabic is the native language of 31 percent of the refugees who entered the US between 2008 and 2016, followed by Nepalese and Somali, spoken by 21 percent and 12 percent, respectively.
To block entry from the designated countries, Trump is likely to tell the State Department to stop issuing visas to people from those nations.
He could also instruct US Customs and Border Protection to stop any current visa holders from those countries from entering the US.
Are Muslims being targeted?
Trump has in the past called for banning all Muslims from entering the US, and forcing the remaining ones to be registered in a national database.
He has also called for shutting down mosques.
Later in his election campaign Trump toned down his rhetoric and said he would focus the restrictions on countries whose migrants could pose a threat, rather than imposing a ban on those from a specific religion.
How many refugees has the US admitted?
The US let in 75,000 refugees in 2016 with 10,000 slots reserved for Syrians.
The administration of former president Barack Obama allowed more refugees after Washington came under pressure from Europe to share the burden of people forced to flee war zones.
According to the UN Refugee Agency, the US was hosting over 273,000 refugees and around 286,000 asylum seekers in 2015.
Washington says that it has settled more than 3 million refugees since the 1970s.
Do Muslims make up the major chunk of refugees going to the US?
In the past 15 years, 46 percent of all refugees who have come to the US were Christian, while 32 percent were Muslim, according to Pew Research Center.
Refugee numbers pale in comparison to the one million legal immigrants that enter the US every year.
And according to a 2013 Pew study, six-in-ten of new legal immigrants were Christian compared to one-in-ten who were Muslim.
Can the US president take these steps legally?
Indeed, the president has the authority to limit refugee admissions and the issuance of visas to specific countries if the administration determines it is in the public interest, said the chief counsel at the US Citizenship and Immigration Services in the Obama administration, Stephen Legomsky.
"From a legal standpoint, it would be exactly within his legal rights."
"But from a policy standpoint, it would be a terrible idea because there is such an urgent humanitarian need right now for refugees.”
What about the refugee children?
Reports of anti-refugee measures have stoked debate on the status of Dreamers – the 750,000 refugees who came to the US as children and have since received resident status.
Obama ordered in 2012 to defer proceeding against illegal immigrants who had entered the country as children. They have also been given temporary residence.
The move was criticised by Trump during his election campaign.
But Trump, who promised to undo the decision, has so far avoided the subject.
How are people reacting to it?
Detractors could launch legal challenges if all the countries subject to the ban are Muslim-majority nations, said immigration expert at UCLA School of Law, Hiroshi Motomura.
It could be argued that the executive orders discriminate against a particular religion, which would be unconstitutional, Motomura said.
"His comments during the campaign and a number of people on his team focused very much on religion as the target."
The move has been attacked by human rights activists.
“To think that Trump’s first 100 days are going to be marked by this very shameful shutting of our doors to everybody who is seeking refuge in this country is very concerning,” the executive director of the National Immigration Law Center, Marielena Hincapié, told The New York Times.
“Everything points to this being simply a backdoor Muslim ban.”
How was Obama's record?
The US deported more than 2.7 million people between 2009 and 2016, the period when Obama was president, according to US Immigration and Customs Enforcement.
His administration insisted that most of these deportees were criminals.