Washington ? It’s gone after the CIA, lax border controls and gaps in the nation’s air-defense system. Now the independent commission that’s investigating the 9-11 attacks is readying what’s likely to be a harsh assessment of Congress for failing to grasp the threat that al-Qaida and other terrorist groups posed.

The panel, which is set to issue its final report July 22, is focusing some of its final investigative work on the role Congress played as warning signs of a possible terrorist attack in the United States piled up in the years before 2001.

“Congress is not blameless in this,” said former New Jersey Gov. Tom Kean, the panel’s chairman. “They held very few hearings on terrorism. You can’t just let Congress off the hook.”

Kean vowed early in the investigation that the panel would look hard at how Congress supervised the intelligence, immigration and defense agencies charged with protecting the nation. But unlike the performance of executive-branch agencies, the issue of congressional accountability seldom arose during the commission’s 12 public hearings.

When the panel has delved into Congress’ actions, its findings have suggested that inertia and pressure politics interfered with national security.

The paucity of information about Congress’ performance amid the growing terrorist threat hasn’t escaped the notice of 9- 11 family members. They’ve pushed the panel hard to press the White House for facts and now want to hear more about why Congress seemed to have been caught unaware by the attacks on the World Trade Center and the Pentagon.

The panel’s final report — whose projected completion date has been moved up several days so as not to coincide with the Democratic National Convention — will be delivered to President Bush and to Congress.

Without members of Congress seeking to highlight gaps in the nation’s defenses, family members point out, the public probably won’t push for change.

“You cannot expect the American people to take that up on their own,” said Kristen Breitweiser of Middletown, N.J., whose husband, Ronald, was killed at the trade center and who’s been a leading 9-11 family advocate.

“What I am saying is we need to find out why all these issues that we apparently have known about for a very long time were not more pressing in Congress,” she said.