The Trump administration says it is cracking down on what it calls “birth tourism” and will instruct consular officers to assess whether women requesting visas to visit the United States are hoping to give birth here to obtain U.S. citizenship for the child.

Starting Friday, the State Department will no longer issue temporary visitor visas to women hoping to travel to the United States for the purposes of having a child, White House officials said in a statement Thursday. The visas — known as B-1/B-2 visas — provide for temporary travel to the United States for tourism, business or medical care.

The State Department said Thursday that consular officers cannot require pregnancy tests to make the determination but would not rule out that a woman’s physical appearance could be taken into consideration. Consular officers will consider “the totality of the circumstances and what comes out in the interview,” a State Department official told a group of reporters on a conference call Thursday, speaking on the condition of anonymity.

The Trump administration has cast the rule as a matter of national security and public safety.

“Closing this glaring immigration loophole will combat these endemic abuses and ultimately protect the United States from the national security risks created by this practice,” White House officials said in a statement, citing a “birth tourism industry” that they argue “threatens to overburden valuable hospital resources.”

“It will also defend American taxpayers from having their hard-earned dollars siphoned away to finance the direct and downstream costs associated with birth tourism,” the White House said.

Immigration attorneys have expressed concerns that the regulation is another brick in what they call Trump’s “invisible wall” — the mass of new rules, policies and regulations the Trump administration has unfurled to make legal immigration more difficult. They also said the rule could be applied in a misogynistic way.

“The rule itself invites discrimination against women,” said Tom Jawetz, a lawyer and the vice president of immigration policy at the Center for American Progress. “If you have consular officers who are looking for opportunities to restrict access to the immigration system, this provides a bit of a tool to do so.”

Eli Kantor, an immigration attorney in Beverly Hills, Calif., said he sees nothing wrong with the apparent intention of the rule, though he does believe it opens up the potential for discrimination against women.

“It makes sense to prevent people from coming to the U.S. just to have a baby who becomes a U.S. citizen,” he said. “But my fear is that by giving them one more tool in their arsenal to vet prospective applicants, it will be that much more difficult for a female applicant to obtain lawful entry into the United States just because she’s female. And I could see potential for abuse depending on how they implement the rule.”

Trump has said he wants to end birthright citizenship for the children of noncitizens, which legal scholars say would require Congress to amend the Constitution. The 14th Amendment affords the right of automatic and permanent citizenship to most people born on U.S. soil.

The White House and the State Department declined to provide examples of security threats linked to birth tourism, data about birth tourism or information about its financial impact.

Of the 5.8 million B-1/B-2 visas issued annually, the State Department estimates that there are thousands of such visa holders who go on to give birth in the United States each year, according to the department official who briefed reporters.

“I don’t have an estimate for you on what this costs U.S. taxpayers,” the official said.

Mike Howell, a senior adviser at the Heritage Foundation, a conservative think tank, estimates that at least 30,000 people come to the United States to give birth every year, and he worries that their U.S. citizen children ultimately could gain access to public benefits. News articles on birth tourism have presented the women typically participating in the practice as affluent Chinese nationals who pay tens of thousands of dollars to patronize “maternity hotels” in California, and are seeking citizenship for their children so as to maximize their educational opportunities.

U.S. Immigration and Customs Enforcement and the Justice Department secured the first conviction in a birth tourism scheme last year in a probe that began under the Obama administration.

Dongyuan Li, 41, pleaded guilty to visa fraud and conspiracy for helping run “You Win USA Vacation Services Corp.,” which charged affluent women in China $40,000 to $80,000 each to obtain visas to come to Southern California to give birth. The company coached more than 500 women to pass their consular interviews abroad and conceal their pregnancies from U.S. Customs and Border Protection once they arrived at the airport, according to ICE and federal court records.

The State Department official on Thursday said that foreign governments might seek to exploit birth tourism, but the official declined to cite examples in which foreign governments have benefited from the practice.

It is unclear exactly how consular officials will determine whether a woman applying for a visa intends to travel to the United States to give birth. The State Department official said that the new rule does not bar all pregnant women from obtaining tourist visas; a pregnant woman traveling for a different purpose, for example, to visit a sick relative, “can still be issued a visa,” the official said. The consideration would apply only to the initial visa application process; many nationalities have access to 10-year, multi-entry tourist visas.

The official also said that not all women would be asked whether they are pregnant — only those for whom an officer has “a specific articulable reason to believe that this applicant is planning to give birth in the United States” would be questioned about their birth plans.

But the official declined to rule out the possibility that consular officers will ask such questions based on a woman’s physical appearance, saying that officers will consider the “totality” of factors. A woman who lists “medical treatment” as her primary reason for travel, for example, could trigger further questions about pregnancy or birth plans, the official said.

Other obstacles could arise upon arrival in the United States, where CBP officers exercise broad discretion to refuse entry to valid visa-holders, and have on several occasions in the past few years turned back heavily vetted visa-holders, such as people who worked for the U.S. government in Afghanistan and secured Afghan Special Immigrant Visas.

A CBP spokesman said the State Department rule will not change the way CBP operates.

“This rule does not affect CBP regulations regarding the admissibility of aliens and it does not otherwise modify the standards enforced by CBP officials at ports of entry,” the spokesman said.

CBP has the authority to deny entry to foreigners traveling with visas under certain circumstances, such as national security concerns.

Acting ICE director Matthew Albence praised the “birth tourism” regulation Thursday as “good sense” and another way to ensure that visitors are not exploiting U.S. law to claim citizenship for their children.

“I think it’s a big problem,” Albence said.