Pakistan, which the Pentagon has repeatedly accused of serving as a sanctuary for terrorists, may be added to the list of seven countries covered by President Donald Trump’s recently-signed executive order limiting immigration from certain Muslim-majority countries.

In an interview with CBS News’s Face the Nation Sunday, White House Chief of Staff Reince Priebus acknowledged for the first time that Pakistan could be added to the list of seven Muslim-majority countries — Iran, Iraq, Libya, Sudan, Yemen, Syria, and Somalia — from where immigration has been halted for at least 90 days while the Trump administration improves the U.S. vetting process.

“The reason we chose those seven countries was, those were the seven countries that both the Congress and the Obama administration identified as being the seven countries that were most identifiable with dangerous terrorism taking place in their country,” Priebus told CBS News.

“Now, you can point to other countries that have similar problems, like Pakistan and others. Perhaps we need to take it further. But for now, immediate steps, pulling the Band-Aid off, is to do further vetting for people traveling in and out of those countries,” added the top White House official.

In an apparent response to backlash from the mainstream media and protesters, Priebus explained that Trump signed the executive order, formally titled, “Protecting the Nation From Terrorist Attacks by Foreign Nationals,” after significant planning.

“We’re not going to advertise to the world that we’re going to put a stop or at least a further vetting on travel in and out of our country from these seven places,” he said, adding, “Some people have suggested, that, well, maybe we should have given everyone a three-day warning. But that would just mean that a terrorist would just move up their travel plans by three days. Identifying too many people in these countries and giving them a heads-up in these countries would only potentially flag the executive order for bad order.”

The White House chief of staff noted that the countries covered by the executive order have been linked to terrorism.

Priebus told CBS News:

These are countries that harbor and train terrorists. These are countries that we want to know who is coming and going in and out of to prevent calamities from happening in this country. We’re not willing to be wrong on this subject. President Trump is not willing to take chances on this subject. He was elected president in many respects because people knew that he was going to be tough on immigration from countries that harbor terrorists. And I can’t imagine too many people out there watching this right now think it’s unreasonable to ask a few more questions from someone traveling in and out of Libya and Yemen before being let loose in the United States.

Two top GOP lawmakers have introduced legislation to officially designate Pakistan a state sponsor of terrorism.

The seven countries covered by Trump’s order are also included in a list of 35 nations and the territories of Gaza and West Bank that the U.S. government officially labeled as specially designated countries (SDCs) that “have shown a tendency to promote, produce, or protect terrorist organizations or their members.”

Although the list was created under George W. Bush, it was also employed by the Obama administration to subject citizens from those countries to additional screening if they are detained by the U.S. Customs and Immigration Enforcement (ICE) agency.

After CNSNews.com reported that the former president had added Israel to the Bush-era list, the Obama administration scrubbed the roll from the only document that publicly mentioned it — a 2011 report compiled by the DHS inspector general.

The list can only be found in archived versions of the report before the Obama administration removed it.

Despite then-ICE Director John Morton alleging that Israel had been added to the list by mistake, documents released in 2012 under a Freedom of Information Act (FOIA) request revealed that the addition had been intentional, a point that has been largely ignored by the media.

Besides the seven countries covered by the Trump national security order, the list of SDCs also included Pakistan and 28 other countries, Saudi Arabia, Egypt, and Turkey, among them.

With the exception of a very few number of nations — namely Israel, the Philippines, and Thailand — the vast majority of the 35 listed countries are predominantly Muslim.

After completely removing the list from the 2011 DHS OIG report, the Obama administration stated: “The specially designated country list as described in Appendix D was created in 2003, is outdated and is being eliminated. The internal procedural guidance has been rescinded and the internal screening criteria and processes are being revised.”