The United States now launches a new investigation into suspected Islamic State group sympathizers almost every day, a senior official said Wednesday, underscoring the increased threat posed by the jihadist group.
Pointing to a significant uptick in cases linked to militants who now control swaths of territory in Iraq and Syria, the official warned Congress of "brinkmanship" over intelligence gathering powers that put national security at risk at a sensitive time.
"We are opening new investigations daily, particularly the ISIL threat," said the senior administration official, using an acronym for the Islamic State group.
"They have a strategy now of encouraging anyone, essentially, to take arms and commit a terrorist attack inside the United States," said the official, speaking on condition of anonymity.
"New individuals" are "popping up pretty much daily on the radar screen in our current threat environment."
The group -- which has gained notoriety for mass executions, torture and sexual slavery -- has vowed to establish a Caliphate based on a strict interpretation of Islamic law.
In the last week alone the Department of Justice has successfully prosecuted individuals in Georgia, Texas and California for providing "material support" to the terror group.
The US official said that agencies like the Federal Bureau of Investigation had to "try to figure out is this the real deal, someone who is going to commit a terrorist act, or not."
"What the FBI is looking for is connectivity, whether they can show that that person has been in touch with one of the terrorists overseas, in Syria or Iraq."
The comments come ahead of a Sunday deadline for the Senate to approve national security laws governing the bulk collection of telephone records, roving wiretaps and "lone-wolf" tracking.
National security investigators "need these types of tools," to do their jobs, the official said.
The National Security Agency will have to start shutting down servers and other equipment linked to the vast dragnet from 3:59 pm (1959 GMT) on Sunday unless new rules pass.
The controversial program scoops up data on calls from millions of Americans who have no connection to terrorism.
Republican 2016 presidential hopeful Rand Paul opposes the program and is blocking passage of measures that would keep the measures in place while limiting how long the government can hold the data.
Officials insist that delay would strip them of important tools to investigate terror suspects and foreign spies.
"There is no good reason to court unnecessary risk," said another senior administration official, speaking on condition of anonymity.