Willie Nelson, an outspoken critic of President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE, is slamming the administration's zero-tolerance policy separating families at the U.S.-Mexico border, saying "Christians everywhere should be up in arms."

"What's going on at our southern border is outrageous," Nelson told Rolling Stone. "Christians everywhere should be up in arms. What happened to 'Bring us your tired and weak and we will make them strong?' This is still the promise land."

Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE announced in early May that the Department of Homeland Security would separate children illegally crossing the U.S.-Mexico border from the adults accompanying them before those adults are prosecuted. The policy is carried out even if a migrant is seeking asylum.

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It has resulted in a sharp influx of children being separated from families at the border in recent weeks. The Associated Press reported on Friday that nearly 2,000 children were separated from their parents from April 19 through May 31, according to figures obtained from the Department of Homeland Security.

The overflow of children has also led the administration to begin erecting a "tent city" in Tornillo, Texas, that will hold 450 beds for children.

Democratic lawmakers have forcefully condemned the policy, which Trump on Friday blamed on Democrats.

The Democrats are forcing the breakup of families at the Border with their horrible and cruel legislative agenda. Any Immigration Bill MUST HAVE full funding for the Wall, end Catch & Release, Visa Lottery and Chain, and go to Merit Based Immigration. Go for it! WIN! — Donald J. Trump (@realDonaldTrump) June 15, 2018

Nelson, who grew up just five hours from the Mexican border, has aimed harsh criticism at Trump. In January, he announced his new album would feature a Trump-inspired song titled, “Delete and Fast-Forward."

Nelson also has previously advocated for pro-immigration policies. He told Rolling Stone in 2014 that helping immigrant children is "a good opportunity for us to show a little bit of humanitarianism and take care of those kids."