President Donald Trump's new ban on travel to the U.S. by citizens from 12 mainly African and Middle Eastern countries is set to take effect Monday amid escalating tension over the president's unprecedented campaign of immigration enforcement.

The new proclamation, which Trump signed on Wednesday, applies to citizens of Afghanistan, Myanmar, Chad, the Republic of Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen. It also imposes heightened restrictions on people from Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela who are outside the U.S. and don’t hold a valid visa.

The new ban does not revoke visas previously issued to people from countries on the list, according to guidance issued Friday to all U.S. diplomatic missions.

However, unless an applicant meets narrow criteria for an exemption to the ban, his or her application will be rejected starting Monday.

Haitian-American Elvanise Louis-Juste, who was at the airport Sunday in Newark, New Jersey, awaiting a flight to her home state of Florida, said many Haitians wanting to come to the U.S. are simply seeking to escape violence and unrest in their country.

“I have family in Haiti, so it’s pretty upsetting to see and hear,” Louis-Juste, 23, said of the travel ban. “I don’t think it’s a good thing. I think it’s very upsetting.”

Many immigration experts say the new ban is designed to beat any court challenge by focusing on the visa application process and appears more carefully crafted than a hastily written executive order during Trump's first term that denied entry to citizens of mainly Muslim countries.