Democratic presidential nominee Joe Biden said he and former President Barack Obama "made a mistake" by failing to achieve comprehensive immigration reform during their eight years in office. 

"It took too long to get right," Biden said during the second and final presidential debate in Nashville. The former vice president also suggested that he would be more effective at addressing the issue than Obama, pledging to deliver an immigration overhaul that would create a pathway to citizenship for more than 11 million undocumented people living in the U.S. 

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"I'll be president of the United States, not vice president of the United States," Biden said. "The fact is I've made it very clear within 100 days, I'm going to send to the United States Congress a pathway to citizenship for over 11 million undocumented people."

Biden has released two immigration plans: The first would reverse the Trump administration's policies, including stopping family separations and ending detention centers for children, while the second would create a pathway for citizenship.

"All of those so-called dreamers, those DACA kids, they're going to be immediately certified again to be able to stay in this country and put on a path to citizenship," Biden said, referring to an Obama-era program known as Deferred Action for Childhood Arrivals that allowed undocumented immigrants who were brought to the U.S. as children to become citizens.

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The former vice president's comment came as President Trump defended his administration's policy of separating children from their parents at the U.S.-Mexico border, days after it was reported that the government had failed to locate the parents of more than 500 children. 

But Trump slammed Biden for creating detention facilities for undocumented immigrants. 

“Who made the cages, Joe?” Trump asked. 

More than 3 million undocumented immigrants were deported during the Obama administration. 

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