Senate Intelligence Committee Chairwoman Dianne FeinsteinDianne Emiel FeinsteinSenate passes 6B defense bill Manchin becomes final Democrat to back bill preventing separation of immigrant families Live coverage: FBI chief, Justice IG testify on critical report MORE (D-Calif.) said Sunday that Sunni extremists taking over parts of Iraq could pose an immediate threat to the United States. 

On CNN’s “State of the Union,” Feinstein said the U.S. knows of at least 100 U.S. citizens who have gone overseas to fight alongside terrorists. 

“This is where I think we need to build our intelligence to see if we can disrupt the plot in this country before it happens,” she said, “because there will be plots to kill Americans.”

Members of the Islamic State in Iraq and Syria (ISIS) have already recruited people in Europe, including Spain and Germany, Feinstein said.

Those Westerners could go back to a European country and if it’s one that waives visas, she said, they could find a way to the U.S.

President Obama said in an interview on CBS’s “Face the Nation” that ISIS poses a “medium and long-term threat” to the U.S, but there are also other groups to monitor. 

This comes just a few days after Islamic jihadists released a video promoting ISIS in which they tried to attract other English-speakers to their fight. House Intelligence Committee Chairman Mike Rogers (R-Mich.) warned about this threat last week.

Federal officials, in fact, arrested and charged two Texas-area men last Wednesday on terrorism-based charges. One was arrested at an airport before boarding a flight bound for Europe. The Justice Department says he was trying to hook up with terrorists in Syria. 

In May, the U.S. confirmed a U.S. citizen committed a suicide bombing in Syria.