Days after yielding to pressure to reverse his policy of separating migrant families at the southern border, President Trump returned Friday to the nativist rhetoric that animated his outsider presidential campaign, casting immigrants as threats to “our citizens.”

Seeking to counter the intense criticism of his border policies, Trump invited families of Americans killed by undocumented immigrants to tell their stories of being “permanently separated” from loved ones.

“These are the stories that Democrats and people that are weak on immigration, they don’t want to discuss, they don’t want to hear, they don’t want to see, they don’t want to talk about,” Trump said at the White House.

The president has been on the defensive this week because of his “zero-tolerance” enforcement policy that has led to at least 2,500 migrant children being separated from their parents. While Trump signed an executive order Wednesday ending the practice, he has bristled at the sympathy directed toward the migrant families and argued without evidence that many of them are criminals and intent on doing harm once in the United States.

“We must maintain a Strong Southern Border,” Trump tweeted Friday morning. “We cannot allow our Country to be overrun by illegal immigrants as the Democrats tell their phony stories of sadness and grief, hoping it will help them in the elections.”

The administration has struggled to implement the hastily drafted executive order, which was intended to end the controversy over family separations by stating that parents and children could be detained together. But the Homeland Security Department interpreted it as meaning they would no longer refer for prosecution the cases of adults illegally crossing the U.S. border with children because of to a lack of space at existing facilities for housing detained families. The Justice Department wanted the prosecutions to continue.

Administration officials met late Thursday and on Friday to try to hash out these differences as well as to come up with a plan for reuniting the migrant families that have already been separated.

At the White House event Friday, Trump and many of the family members who spoke criticized what they called one-sided media coverage that does not focus on their stories.

“We weren’t lucky enough to be separated for five days or 10 days; we’re separated permanently,” said Laura Wilkerson, whose son Josh was killed in 2010. “Any time we want to see or be close to our kids, we go to the cemetery, because that’s where they are. We could never speak to them, we can’t Skype with them.”

The president blamed Democrats for what he called weak immigration laws and policies that treat those in the country illegally too leniently, even though Republicans control Congress and failed this week to pass an immigration bill out of the House because of opposition from GOP members. Trump railed against the MS-13 gang, heroin from outside the United States, and so-called “catch and release” immigration enforcement.

Trump also said he does not believe research that shows undocumented immigrants are less likely to commit crimes than ­native-born citizens, but did not specify how he came to that conclusion.

“I always hear that, ‘Oh, no, the population’s safer than the people that live in the country,’ ” Trump said. “You’ve heard that, fellas, right? You’ve heard that. I hear it so much, and I say, ‘Is that possible?’ The answer is it’s not true. You hear it’s like they’re better people than what we have, than our citizens. It’s not true.”

The president also falsely claimed that 63,000 Americans have been killed by illegal immigrants since the Sept. 11 terrorist attacks. The number appears to come from a 2006 blog post from Rep. Steve King (R-Iowa), who advocates limiting immigration, that was based on conjecture, not statistical evidence.

Trump’s comments on immigration this week have roiled the debate in Congress, where House Republican leaders were attempting to pass legislation that could satisfy conservatives and moderates.

On Friday morning, Trump tweeted that Republicans should stop “wasting their time” on immigration, suggesting they put off efforts to pass legislation until after the November elections, when he predicted more GOP members of Congress will be elected.

Trump’s comments came after Republican leaders in the House abruptly postponed a vote Thursday on a broad immigration bill intended to unite GOP moderates and conservatives, acknowledging they lacked the votes to pass the measure despite the growing uproar over separating migrant families at the border.

Trump’s tweet, GOP aides said, could make the task of corralling votes for the bill significantly more difficult, though House Republican leaders said negotiations would continue. The House defeated a bill supported by conservatives on Thursday.

“Republicans should stop wasting their time on Immigration until after we elect more Senators and Congressmen/women in November,” Trump wrote. “Dems are just playing games, have no intention of doing anything to solves this decades old problem. We can pass great legislation after the Red Wave!”

Majority Whip Steve Scalise (R-La.) said Trump was “expressing his frustration” at a lack of Democratic involvement on the issue and that efforts will continue to find enough votes to pass a bill. But Scalise acknowledged it would be “an uphill fight.”

“We’re going to move forward,” he said. “We’re going to have a vote. . . . It would be nice if you had at least one Democrat who was willing to vote for a bill that secures America’s border, and so far none have been willing to do that.”

Responding to Trump’s latest tweets, Democrats — who are optimistic they will pick up seats in both chambers of Congress in November — said it was Trump who is standing in the way of immigration reform and trying to create a political issue. They have expressed frustration that the Republican bills were crafted without their input.

The bill set to be voted on next week would provide $25 billion for Trump’s long-sought border wall, offer a pathway to citizenship to young undocumented immigrants known as “dreamers” and keep migrant families together in detention centers.

Rep. Bradley Byrne (R-Ala.), a member of the whip team in the House, said Trump could make a difference in passing legislation if he were more emphatic about what he wants.

“If the president said to a given bill, ‘That’s my bill, that’s the one I want,’ I think that would have a pretty significant impact on our discussions,” Byrne said. “But he hasn’t done that yet, and so we’re continuing to work without that.”

Despite the GOP leadership’s vows to fight on, some Republicans were openly skeptical about their ability to achieve success in the wake of Trump’s latest tweets.

“Game over,” Rep. Mark Sanford (R-S.C.) said during an interview on CNN. “It takes the wind out of the sails in what might have been a fairly productive week in terms of looking for compromise. I don’t know how it happens, because if you look at how contentious this issue is, how much emotion there is, without the president being out front — without the president having legislators’ backs — there’s no way they’re going to take the risks that would be inherent in a major reform bill.”

GOP aides noted the difficulties. The chances of a bill passing are “not good, and worse with the POTUS tweets,” said one aide, who requested anonymity to speak candidly about the sensitive issue. Another said Trump would be to blame if legislation fails.

The president seemed unconcerned, having already turned his attention to November’s midterm elections.

“Elect more Republicans in November and we will pass the finest, fairest and most comprehensive Immigration Bills anywhere in the world,” Trump tweetedFriday. “Right now we have the dumbest and the worst. Dems are doing nothing but Obstructing. Remember their motto, RESIST! Ours is PRODUCE!”

Erica Werner, Sean Sullivan and Felicia Sonmez contributed to this report.