By Andrew Goudsward, Sarah N. Lynch

WASHINGTON (Reuters) -The FBI is concerned about the possibility of an organized attack in the United States similar to the one that killed scores of people at a Russian concert hall last month, the bureau’s director plans to tell a House of Representatives panel on Thursday.

“Looking back over my career in law enforcement, I’d be hard-pressed to think of a time where so many threats to our public safety and national security were so elevated all at once,” Christopher Wray is set to tell lawmakers at budget hearing on Thursday.

“But that is the case as I sit here today.”

The March 22 attack on a concert hall in a Moscow suburb killed at least 144 people, the deadliest in Russia in 20 years. A branch of the Islamic State militant group claimed responsibility, but Russian President Vladimir Putin, without citing evidence, has sought to blame Ukraine.

U.S. officials have been worried about the possibility of an attack carried out by an individual or small group inspired by the war between Israel and Hamas in Gaza.   

But the FBI is growing concerned about a more coordinated attack following the concert massacre in Russia, Wray will say during testimony. 

At the end of the 2023 fiscal year, the FBI had 4,000 international terrorism investigations open, according to Wray’s prepared testimony.

Of increasing concern “is the potential for a coordinated attack here in the homeland, akin to the ISIS-K attack we saw at the Russia Concert Hall a couple weeks ago,” Wray will tell lawmakers.

Wray plans to cite the law enforcement agency’s concerns about terrorism to help persuade lawmakers to boost funding for the FBI, though he is likely to face strong pushback from Republicans on the panel.

The FBI has become a prime target for Republican former President Donald Trump and his allies, with Trump alleging the bureau has unfairly targeted him while going soft on his political enemies.

He has called on Congress to slash the agency’s funding, and he has referred to the Justice Department and its FBI component as “vicious monsters.”

Wray, who was appointed by Trump in 2017, will ask lawmakers to help get the bureau’s budget “back on track” after its fiscal 2024 budget fell $500 million short of what was needed to sustain its efforts.

Wray also plans to press lawmakers to renew a U.S. surveillance program set to expire this month, calling it an indispensable tool against U.S. adversaries. A modest overhaul of that program was blocked in the House on Wednesday amid concerns from members of both parties that it did not go far enough in curbing the government’s surveillance powers.

“It’s critical in securing our nation, and we’re in crunch time,” Wray plans to tell lawmakers.

Trump and his allies have called for the surveillance program to be shut down, after a different provision of the law – known as the Foreign Intelligence Surveillance Act, or FISA – was used to intercept communications with one of his 2016 campaign advisers.