ABC News is unsettled by the impact of NBC Nightly News’s Tom Llamas during his first month as host, an industry source has claimed. 

The worries arise from the fact that the former World News Tonight weekend anchor is gaining popularity among younger audiences, potentially catching up to ABC News star David Muir, 51, according to an insider.

Llamas, 46, stepped in for longtime host Lester Holt early last month.

He has been narrowing the viewer gap in the highly sought-after 25-54 age group, making it the closest it has been in five years, and has also made strides with the A18-49 demographic.

Three straight weeks of growth under Llamas in terms of total viewers have also caught the attention of ABC News bosses, the source alleged.

“There is increasing concern that Muir’s apparent successor is already showing promising signs, and it is beginning to appear in the viewership ratings,” the insider stated.

Muir, meanwhile, is notoriously private. He offered a rare sit-down with People in late May days before Llamas’ start, the insider pointed out. 

‘Between this, the disastrous Terry Moran exit and GMA3 being completely reworked, anxiety is high at ABC,’ the insider said.

ABC News is unsettled by recent strides made by NBC Nightly News’s Tom Llamas during his first month as host, an industry source has claimed

David Muir, pictured in April, presents the United States’ most popular news broadcast. His lead is a significant one, meaning Llamas faces an uphill struggle to overtake him  

Moran was fired from ABC after 27 years in June for an X post branding Donald Trump and his aide Stephen Miller ‘world class haters.’ 

GMA3 – the third hour of ABC’s Good Morning America – is now set for the ax after struggling to retain viewers. 

But it’s not all bad news for ABC.

Despite a promising start, Llamas still has a long way to go before he catches up with Muir, who is the United States’ most popular newscaster.

Muir’s World News Tonight commands a far bigger overall audience and remains considerably more popular among younger viewers.

His lead over Nightly News grew again from May and June, the new Nielsen numbers showed – from 7.24 million to 7.308 million in total viewers. 

NBC, meanwhile secured 5.751 million total viewers, up from last week and this time last year.

World News Tonight’s 1.58 million-viewer lead over NBC is its largest in a second quarter in 30 years. 

In the all-important 25-54 demo, Nightly News pulled in 840,000 viewers to Muir’s 1.01 million.

In another encouraging sign, Nightly delivered a five-week high in the A25-54 demo, suggesting any battle by Llamas to beat Muir will be an uphill one.  

A high-level industry insider trashed claims that Llamas is unnerving ABC bosses.

‘The reality is “World News Tonight” is beating Nightly News by nearly 2 million viewers on many nights and just had the biggest June win over Nightly News in 30 years,’ the source told Daily Mail.

‘While NBC News remains focused on their transition from Lester Holt, ABC News remains focused on the news,’ the source added.   

But there are signs that transition from Holt to Llamas is going well.

Llamas has managed to avoid a drastic ratings drop since taking over from his predecessor, a well-liked industry veteran known for his straight-down-the-middle reporting.

Third place rival CBS News has seen embarrassing slumps since its former star anchor Norah O’Donnell quit her seat in January.

Llamas, seen here with wife Jennifer, succeeded longtime Nightly News host Lester Holt last month

Despite Muir’s sizable lead on both fronts, Llamas’s was the only evening newscast to see grow in both total and demo viewers year-over-year and week-over-week. 

Muir, meanwhile, has been a primetime mainstay for 11 years. 

He succeeded Diane Sawyer in 2014 when World News Tonight still trailed NBC in primetime.  

Muir has held the primetime crown for the past three years running, after erasing that gap in a matter of years. 

The life-long newsman is only 51 and is seen as having a lengthy career at the top ahead of him. 

Llamas, however, could repeat history with another swing as he looks looks poised to expand his share of the evening news market.

He told The Washington Post in June that he ‘want[s] to be number one’ in primetime.

He conceded, however, that his goal was a lofty one.

‘It’s not easy,’ Lamas said. ‘But it’s something I think we can do.’

He admitted, ‘It’s not going to happen in a month.’

Daily Mail contacted ABC News for comment.