The FBI must scramble to keep up with increasingly sophisticated terrorists and improve its ability to gather intelligence on global threats to the nation's security, according to an outside review released Wednesday.

The report said the FBI has made significant strides since the Sept. 11 terror attacks, including sharing information with other law enforcement agencies. But it said there's still room for improvement, especially at a time of emerging new threats such as the Islamic State and Westerners joining militant fighters in Syria.

"These threats are not just knocking on the door. They're in the room," said former Rep. Timothy Roemer, a member of the original 9/11 commission who helped prepare the new 127-page analysis.

The report was ordered by Congress to assess the FBI's performance on counterterrorism national security matters, and its authors said they hoped it would serve as a blueprint for improvement. It was also intended to gauge how well the 9/11 commission's recommendations in a 2004 report are being carried out.

It was released as FBI Director James Comey went to Capitol Hill to defend an $8.48 billion budget request that seeks extra funding for cyber investigations, among other changes.

Though largely positive about the FBI's transformation over the last decade, the report identified several weakness, including a need for better intelligence analysis and collection. The FBI's staff of intelligence analysts should be valued as part of a "professionalized workforce" with specific requirements in training and education and access to better technology.

"This imbalance needs urgently to be addressed to meet growing and increasingly complex national security threats, including from adaptive and increasingly tech-savvy terrorists, more brazen computer hackers, and more technically capable, global cyber syndicates," the report states.

The report looked at five terror plots and attacks in the last few years, including the 2009 Fort Hood shooting and the 2013 Boston Marathon bombing. It identified lapses in communication and coordination among different offices of the FBI, though the report said it could not say whether law enforcement could have detected the plots earlier with better collaboration.

Even though the FBI cultivates confidential sources for intelligence purposes, no human sources provided information to stop or prevent any of the five plots, it found.

In some cases, information that may have been useful -- such as a 2012 outburst at a religious center by Boston Marathon bomber Tamerlan Tsarnaev -- never made it to the FBI or was not analyzed carefully enough. Intelligence programs in New York and Denver also failed to identify Najibullah Zazi, an Afghan-American cab driver convicted in a thwarted plot to blow up New York City's subway system, the report said.

The report also said frequent leadership changes slow down the pace of improvement, and that the FBI needs better coordination with the private sector and other agencies to deal with cyber threats.

Because of constitutional and legal challenges to its intelligence collection, the FBI must ensure that it received "state-of-the-art tools" from Congress.

Comey said he supports most of the conclusions, though he said he disagreed with the recommendation that the FBI should not have a role in a new White House initiative to counter the radicalization of Americans through community outreach.

"I think there is an important role for the FBI to play," Comey said, although he added that role wouldn't touch on matters of religion.