Wendell P. Weeks of Corning listens to President Trump during a meeting with business leaders in the Roosevelt Room of the White House on Jan. 23, 2017. (Matt McClain/The Washington Post)

The Trump administration plans to start vetting would-be immigrants and visitors to the United States based partly on their opinions and ideology, and will immediately cease the resettlement of Syrian refugees in the United States, according to a draft executive order leaked Wednesday to civil rights advocates and obtained by The Washington Post.

The order, if enacted, would signal the beginning of the “extreme vetting” that President Trump promised on the campaign trail, as well as partial implementation of the “Muslim ban,” according to civil rights advocates.

The order calls for an immediate 30-day halt to all immigrant and nonimmigrant entry of travelers from certain countries whose citizens “would be detrimental to the interests of the United States.” Once signed, it would allow those with visas to be turned away at U.S. airports and other entry points.

The countries — designated under several provisions of law that have already singled them out for terrorism links — include Iraq, Iran, Syria, Yemen, Sudan, Libya and Somalia. While all are Muslim-majority countries, the list — and the ban — do not include Saudi Arabia, Egypt, Jordan and numerous other Muslim-majority countries.

Additionally, all refu­gee admission and resettlement would be halted for 120 days — and until further notice, from Syria — while vetting procedures are reviewed. Once restarted, annual refu­gee admissions from all countries would be cut from the currently authorized level of 100,000 to 50,000.

Asked Wednesday about the draft, White House press secretary Sean Spicer said actions dealing with refugees and other U.S. admissions would be signed later in the week, and “as we get into implementation of that executive order, we will have further details.” Trump’s “guiding principle,” he said, is to prevent entry to “people who are from a country that has a propensity for doing harm.”

Civil rights and refu­gee advocates immediately expressed alarm over the policies, and said that the news has thrown groups that handle refu­gee resettlement and immigrant rights — including U.N. agencies — into disarray.

“These actions taken by Donald Trump are tantamount to a Muslim ban,” Abed A. Ayoub, the legal and policy director for the American-Arab Anti-Discrimination Committee, said during a Wednesday conference call with refu­gee and immigrant advocates and journalists. “Regardless of how they try to frame it . . . this is the Muslim ban that was promised by him on the campaign trail.”

In justifying its actions, the order states that “hundreds of foreign-born individuals have been convicted or implicated in terrorism-related crimes since September 11, 2001.”

Most terrorist or suspected terrorist attacks since 9/11 have been carried out by U.S. citizens. The 9/11 hijackers hailed primarily from Saudi Arabia, as well as the United Arab Emirates, Egypt and Lebanon — all U.S. allies, and none of which would be affected by the immediate ban.

Since the emergence of the Islamic State in 2014, federal prosecutors have also charged 106 people in connection with the group, many of them for planning to travel from the United States to Syria or Iraq to join it. It is unclear how many were foreign-born.

Along with ending all Syrian refu­gee resettlement “until such time as I have determined that sufficient changes” have been made to vetting programs, Trump’s order directs the secretaries of state and defense to deliver within 90 days a plan to provide “safe areas” inside Syria and “in the surrounding region” where displaced Syrians can await “firm resettlement, such as repatriation or potential third-country resettlement.”

Waivers to the ban on refugees and overall priority for admission would be given to those claiming religious persecution, “provided that the religion of the individual is a minority religion in the individual’s country of nationality.”

Some Republican lawmakers have called for special protection for Christians, Yazidis and other religious minorities fleeing the Islamic State, although the vast majority of those killed and persecuted by the militants are Muslims.

Additional provisions under the order, entitled “Protecting the Nation from Terrorist Attacks by Foreign Nationals,” would require all travelers to the United States to provide biometric data on entry and exit from the country, instead of current entry-only requirements. It would immediately suspend a waiver system under which citizens of certain countries where U.S. visas are required do not have to undergo a face-to-face interview at a U.S. consulate.

The entry-exit requirement resembles provisions previously in place under the National Security Entry-Exit Registration System (NSEERS), the registry program that targeted mostly Muslim men and which the Department of Homeland Security ultimately found to be redundant with existing protocol, and ineffective for identifying terrorists.

As president, Barack Obama dismantled the legal framework for the NSEERS program. But Shoba Wadhia, a clinical professor of law at Penn State University and the director of its Center for Immigrants’ Rights Clinic, described the draft executive order’s provisions as “NSEERS on steroids.”

“It definitely far exceeds what we saw with NSEERS,” she said. “NSEERS itself was a complete disaster. It had no security value; it really overwhelmed government offices and officials who were unprepared.”

A key question for U.S. courts, if the order is challenged, will be whether the new policies exceed the reasonable boundaries of the president’s executive authority on immigration or violate portions of the Constitution, legal experts say.

The draft order instructs the U.S. government to screen visa applicants for their ideologies. “In order to protect Americans, we must ensure that those admitted to this country do not bear hostile attitudes toward our country and its founding principles,” the draft order reads.

The order says the United States should screen visa applicants to block access to those “who would place violent religious edicts over American law” and those who “engage in acts of bigotry or hatred” including “honor” killings, violence against women, and persecution on the basis of religion, race, gender and sexual orientation, a description that human rights groups say also appears to be geared toward Muslims, without naming Islam explicitly.

Joanne Lin, the senior legislative counsel to the American Civil Liberties Union, said the wording “raises the prospect of ideological tests for admission to the U.S.” It could potentially be used to screen out critics of U.S. policy, and could violate Americans’ First Amendment right “to hear from speakers that oppose the government’s official views.”

In addition to questions about what they will do, whom they will see and how they will pay for a U.S. visit, visa applicants can be asked if they seek U.S. entry to engage in terrorism or other illegal activities, and whether they have committed or been convicted of crimes. Those requesting immigrant or permanent residence status are also asked about Communist Party membership.

This article has been updated to correct the spelling of the last name of Joanne Lin, the senior legislative counsel to the American Civil Liberties Union.