WASHINGTON — The Supreme Court is allowing the Trump administration to implement its policy of requiring asylum seekers who arrived at the U.S. southern border to stay in Mexico while their applications are pending.

The Trump administration asked the high court to block a lower court's injunction preventing officials from enforcing its "return-to-Mexico" policy, which immigrant advocates have denounced as inhumane. Administration officials argued the policy has been "enormously effective" in staving off the flow of Central American migrants coming from the southern border.

Solicitor General Noel Francisco argued that if the injunction were allowed to take effect, many of the more than 25,000 asylum seekers who were sent to Mexico "will rush immediately" to the United States. Wednesday's decision lifts that injunction, keeping the policy in place while legal papers are filed seeking full review of the case by the Supreme Court and while the high court decides whether or not to accept the case.

"A surge of that magnitude would impose extraordinary burdens on the United States and damage our diplomatic relations with the government of Mexico," Francisco argued.

Attorneys representing several asylum seekers said these claims, "even if true," do not justify placing thousands of migrants in danger under the policy.

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"Indeed, the U.S. State Department itself has recognized the victimization of migrants in Mexico, including kidnappings, extortion, and sexual violence ... Asylum seekers face extreme harm from Mexican cartels, corrupt government officials, and the same Central American gangs that many fled their home countries to escape," attorneys at the American Civil Liberties Union argued.

The news spread quickly across the border into Tijuana, one of three Mexican border cities that would’ve been impacted had the lower court’s ruling.

“This means that everything will remain the same and that people will continue to be exposed at the border," said Esmeralda Siu, coordinator for the Coalición Pro Defensa del Migrante, a collective of migrant shelters in the area. "It’s not like they’re safe here."

The ACLU cited numbers from Human Rights First, which said there have been least 1,001 publicly reported cases of violent crimes against migrants who were sent back to Mexico under the policy.

The Department of Homeland Security in January rolled out the policy, officially called Migrant Protection Protocols, to deter asylum seekers from illegally crossing the southern border. Applicants have been sent back to seven Mexican border cities, from Tijuana to Matamoros.

Last month, a three-judge panel for the 9th Circuit Court of Appeals ruled 2-1 that the policy violates federal immigration law allowing asylum seekers who have expressed "credible fear" of persecution to remain in the United States. Under the policy, asylum seekers may come back to the United States only to appear for their court hearings. Immigration officials are instructed not to ask asylum seekers whether they fear returning to Mexico.

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The policy "has had serious adverse consequences" to asylum seekers who have shown proof that they faced discrimination, sexual and physical violence, corrupt law enforcement, hunger and homelessness after returning to Mexico, 9th Circuit Court Judge William Fletcher wrote.

The Trump administration did not provide evidence to back its claims that there is little danger to asylum seekers in Mexico and that any type of violence they may face does not amount to persecution. On the contrary, Fletcher notes, several asylum seekers have described threats and violence directed at them because of their nationality.

"This evidence in the record is enough — indeed, far more than enough — to establish that the Government's speculations have no factual basis," Fletcher wrote.

The case stemmed from a lawsuit filed last year by immigration advocates and several migrants who were sent back to Mexico under the policy. A federal district judge in California issued a preliminary injunction. The Trump administration promptly appealed and asked for an emergency stay on the ruling. The request was granted, effectively keeping the policy in place while the case is pending.

The policy is now in effect in California, Arizona, New Mexico and Texas.

Last week, the 9th Circuit issued a separate order that would stop the policy in California and Arizona, where the appeals court has jurisdiction, starting Thursday.

Contributing: Rick Jervis, USA TODAY; Rafael Carranza and Nick Oza, Arizona Republic.