2024 election updates: Trump blasts Harris ahead of her trip to the border

The Secret Service informed Trump’s campaign it wouldn’t be able to accommodate his outdoor rally in Wisconsin on Saturday due to manpower issues, according to a source briefed on the situation.

The campaign wanted to have a rally at an airport hangar, but due to the Secret Service being stretched thin with the U.N. General Assembly in New York, it didn’t have the number of agents necessary to secure that site. A source said Secret Service personnel and equipment are being pushed to their limits to sustain the current operational tempo.

Trump’s detail is akin to those of President Joe Biden and Harris, with the exception of Defense Department assets on their details, and the agency wasn’t built to handle these increasing needs, according to a source familiar with the planning.

"Former President Donald Trump is receiving heightened levels of U.S. Secret Service protection and our top priority is mitigating risks to ensure his continued safety at all times,” Anthony Gugliemi, Secret Service chief of communications, said. “Out of concern for operational security, we cannot provide specific details about resources allocated for event security or communications between agency personnel and our protectees."

The Trump campaign hasn’t responded to ABC News’ request for comment.

ABC News' Luke Barr

Trump blasted Harris' record as he spoke about immigration at Trump Tower in New York, .

"Kamala Harris will be visiting the southern border that she has completely destroyed, from what I understand, tomorrow," Trump said. "Why would she go to the border now, playing right into the hand of her opponent? I mean, you take a look at this -- why would you do that? There can be no justification for what she’s done."

Trump is going through a lengthy list of his grievances with Harris and continued to demonize migrants.

In a last-minute addition to his schedule, Trump's campaign announced that he will deliver remarks Thursday at Trump Tower at 4:30 p.m. ET.

The campaign didn't disclose the topic of his remarks, but they will happen on the same day that New York City Mayor Eric Adams has been charged with five counts connected to improper campaign contributions, according to a sweeping indictment unsealed Thursday morning.

This weekend, Trump will campaign in Michigan and Wisconsin.

-ABC News' Lalee Ibssa, Soorin Kim and Kelsey Walsh

Describing her decision not to take the stage at the Republican National Convention, Melania Trump pointed to the letter she penned following Trump's assassination attempt in Butler, Pennsylvania.

"It was my decision. I think was just the time. I think was the right time in, days before I wrote a beautiful letter to America, yes. And I think in one way, that letter was my speech," she said in an interview that aired on Fox & Friends on Thursday morning.

Like her husband, Melania Trump blamed rhetoric from Democrats and people in the media as reasonings for why she feels there has been targeted violence against the former president.

"This is not normal, and is it really shocking that all this outrageous violence goes against my husband? Especially that we hear the leaders from the opposition party and mainstream media branding him as threat to democracy, calling him vile names," she said. "They're only fueling a toxic atmosphere and giving power to all of these people that they want to do harm to him. This needs to stop. This needs to stop. The country needs to unite."

Recounting the moments she heard about Trump's first assassination attempt, Melania Trump said that she couldn't get ahold of Trump or the Secret Service initially.

"First, the Secret Service was not available too, because they were with him, right? And then after that, I got the Secret Service on the phone, and they said that he's OK. We are in on the way to the hospital," she said.

She also talked about having to tell their son, Barron, about the attack.

"He was outside playing sport, and he rushed in, and was very, very difficult," she said.

ABC News' Lalee Ibssa, Soorin Kim and Kelsey Walsh