US President Donald Trump is expected to sign several executive orders on Wednesday restricting immigration from Syria and six other Middle Eastern or African countries, according to several congressional aides and immigration experts briefed on the matter.
In addition to Syria, Trump's orders are expected to temporarily restrict access to the United States for most refugees.
Another order will block visas from being issued to those from Iraq, Iran, Libya, Somalia, Sudan and Yemen, said the aides and experts, who asked not to be identified.
The restrictions on refugees are likely to include a multi-month ban on admissions from all countries until the US State Department, and the US Department of Homeland Security can make the vetting process more precise.
TRT World's Jon Brain give more details.
Trump was expected to sign the orders at the headquarters of the US Department of Homeland Security, whose responsibilities include immigration and border security.
In his tweet late on Tuesday, Trump said: "Big day planned on national security tomorrow. Among many other things, we will build the wall!"
The border security measures likely include directing the construction of a border wall with Mexico and other actions to reduce the number of illegal immigrants living inside the United States.
White House spokesman Sean Spicer said on Tuesday that the US State and Homeland Security departments would work on the vetting process once Trump's nominee to head the US State Department, Rex Tillerson, is confirmed.
Both Trump and his nominee for attorney general, US Senator Jeff Sessions, have said they would focus immigration restrictions on countries whose refugees could pose a threat rather than place a ban on people who follow a specific religion.
TRT World's Jon Brain adds more from Washington.
To block entry from the designated countries, Trump is likely to instruct the US State Department to stop issuing visas to people from those nations, according to sources familiar with the visa process. He could also instruct US Customs and Border Protection to stop any current visa holders from those countries from entering the United States.
Other measures may include directing all agencies to finish work on a biometric identification system for non-citizens entering and exiting the United States and a crackdown on immigrants fraudulently receiving government benefits, according to the congressional aides and immigration experts.