President Donald Trump signed a proclamation on Wednesday evening banning citizens of 12 countries from entering the U.S., citing threats to national security.

The ban will go into effect on Monday.

“Today (Wednesday), President Donald J. Trump signed a Proclamation to protect the nation from foreign terrorist and other national security and public safety threats from entry into the United States,” said a White House statement.

The proclamation “fully restricts and limits” the entry of nationals from 12 countries found to be deficient in screening and vetting and determined to pose a very high risk to the U.S.

The countries are Afghanistan, Burma, Chad, the Republic of the Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan, and Yemen.

Additionally, the proclamation “partially restricts and limits” the entry of nationals from seven countries “who also pose a high level of risk” to the U.S. The affected countries are Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan, and Venezuela.

The White House statement, however, noted that the proclamation includes “exceptions for lawful permanent residents, existing visa holders, certain visa categories, and individuals whose entry serves U.S. national interests”.

The U.S. government explained that the restrictions and limitations imposed by the proclamation “are necessary to garner cooperation from foreign governments, enforce our immigration laws, and advance other important foreign policy, national security, and counterterrorism objectives”.

Mr Trump said, “We will restore the travel ban, some people call it the Trump travel ban, and keep the radical Islamic terrorists out of our country that was upheld by the Supreme Court.”

In his first term, Mr Trump successfully implemented a travel ban that restricted entry from several countries with inadequate vetting processes or significant security risks.

The Supreme Court upheld the travel ban, ruling that it “is squarely within the scope of presidential authority” and noting that it is “expressly premised on legitimate purposes”.

The White House statement pointed out that it “is the president’s sacred duty to take action to ensure that those seeking to enter “our country will not harm the American people”.

“After evaluating a report submitted by the Secretary of State, in coordination with other cabinet officials, President Trump has determined that the entry of nationals from certain countries must be restricted or limited to protect U.S. national security and public safety interests,” it added.