WASHINGTON (AP) — President Donald Trump and Democratic critics traded outraged, sometimes plainly false accusations about immigration as the debate over "lost" children and the practice of separating families caught crossing the border illegally reached a new boiling point.

The White House on Tuesday wrongly blamed Democrats for forcing Trump's administration to separate children from parents. Liberal activists and others, including some from media outlets, tried to highlight the issue by tweeting photos of young people in steel cages that actually were taken during the Obama administration. Others seized on reports the government had "lost" more than 1,000 children, though that wasn't quite the case.

It all comes just in time for the midterm elections as Republicans and Democrats try to rally core voters by pointing fingers at one another. Trump won the presidency promising to build a wall along the southern border and end illegal immigration, and the White House believes stressing the same issues will drive voters to the polls and help the GOP hang on to their majorities in the Senate and House.

The White House is "really beating the immigration drum in the lead-up to the midterm elections as a rallying cry and as a way of mobilizing voter support for Trump and the candidates that he chooses," said Doris Meissner, a senior fellow at the nonpartisan Migration Policy Institute and former commissioner of the U.S. Immigration and Naturalization Service during the Clinton administration. "It does seem to provoke a ratcheting up across the board."

Indeed, the situation grew so hostile over the holiday weekend that the president's elder daughter, White House adviser Ivanka Trump, came under fire for tweeting a photo of herself and her youngest son in their pajamas Sunday morning.

"Focus on what is before you, on what you can control and ignore the trolls!" she later wrote.

During a White House conference call Tuesday, senior adviser Stephen Miller contended "the current immigration and border crisis" is "the exclusive product of loopholes in federal immigration law that Democrats refuse to close."

That was after Trump lit up social media over the weekend by falsely claiming there was a "horrible law" that separates children from their parents after they cross the border illegally. He had said previously that "we have to break up families" at the border because "the Democrats gave us that law."

But there's no law mandating that parents must be separated from their children, and it's not a policy Democrats have pushed or can change alone as the minority in Congress. The tactic's increased use is being driven by Trump's administration, which recently announced a new "zero-tolerance policy" in which it will press criminal charges against all people crossing the border illegally, even if they have few or no previous offenses. More children are expected to be separated from their parents as a result.

A Customs and Border Protection official told lawmakers last week that 658 children had been separated from their parents at the border from May 6 to May 19 as the parents face charges. That's in addition to hundreds more who were estimated to have been removed from their parents since October.

The practice has drawn condemnation from Trump critics, who have long accused him of supporting inhumane policies in his efforts to crack down on illegal immigration.

"He actually called the practice horrible. If he thinks it's so horrible then he ought to just end it and not make the children a negotiating tool," said Lee Gelernt, deputy director of the American Civil Liberties Union's Immigrants' Rights Project.

"It's never a good idea to separate small children from their parents," said Rep. Carlos Curbelo, R-Fla. "I cannot defend that, nor do I wish to."

Curbelo is a leader of GOP lawmakers trying to force House immigration votes next month over leaders' objections.

Trump foes made their own missteps in the debate.

Over the weekend, some critics of the policy tweeted photos of young-looking immigrants at the U.S.-Mexico border in steel cages and blamed the Trump administration for separating immigrant children from their parents. The problem: The photos were taken by The Associated Press in 2014, when Barack Obama was in office, and the photo captions reference children who crossed the border as unaccompanied minors.

How or why the story resurfaced on social media four years after it was published was unclear. But Trump seized on the error.

"Democrats mistakenly tweet 2014 pictures from Obama's term showing children from the Border in steel cages. They thought it was recent pictures in order to make us look bad, but backfires," Trump tweeted Tuesday. "Dems must agree to Wall and new Border Protection for good of country ... Bipartisan Bill!"

It's unclear what "Bipartisan Bill!" Trump might have been referring to.

Congress is heading toward an immigration showdown in the House as Republican moderates force a June vote on legislation to protect young "Dreamer" immigrants and beef up border security.

GOP leaders are trying to stop the bill, which has robust support from Democrats and some Republicans. They're worried any legislation that smacks of "amnesty" for immigrants in the U.S. illegally would dampen conservative enthusiasm ahead of the midterms.

Instead, House Speaker Paul Ryan and his leadership team are trying to put together an alternative approach that most Republicans would support. But finding common ground remains difficult. Trump so far has not engaged in the Capitol Hill debate, even as he repeatedly insists Congress must act.

Also making the rounds on social media over the holiday weekend: Allegations that children placed in custody have been "lost" by federal authorities, which officials say isn't the case.

The allegation, which sparked #WhereAreOurChildren on Twitter, grew out of testimony in April by a federal official that the government had lost track of nearly 1,500 unaccompanied minor children it placed with adult sponsors in the U.S.

An official from the Health and Human Services Department told a congressional hearing last month that his department placed follow-up phone calls from October to December to U.S. households that were sponsoring minors who crossed the border without their parents. They reached 86 percent of the children or sponsors, but the department could not verify the whereabouts of 1,475. In some cases, sponsors simply didn't respond to the follow-up phone call, not surprising because many are themselves in the U.S. illegally and reluctant to speak to authorities.

"If you call a friend and they don't answer the phone, you don't assume that they've been kidnapped," HHS' Steven Wagner said.

Officials said Tuesday they are planning more thorough screening of both minors and their sponsors, including a fingerprint background check of every sponsor.

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Associated Press writers Anne Flaherty and Lisa Mascaro in Washington, Elliot Spagat in San Diego, and Alan Fram in Homestead, Florida, contributed to this report.

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Follow Colvin on Twitter at https://twitter.com/colvinj.