Given America’s long-running battle with Islamist terrorists — a battle that won’t end soon — we need to know which countries support terrorists under the table. Especially when those countries are supposed to be allies.

So it’s bizarre that the U.S. government still refuses to release the infamous 28 pages of the 2002 report of the joint congressional inquiry into the 9/11 attacks. These classified pages supposedly implicate some Saudi officials in assisting the hijackers.

As former Sen. Bob Graham, D-Fla., co-chairman of the inquiry, recently wrote in the Washington Post, in urging that the pages be released: “Should we believe that the 19 hijackers (15 of them Saudi), most of whom spoke little English and had never before visited the United States — acted alone? Did the hijackers have foreign support? If so, who provided it?”

Why is critical information that might answer these questions still being suppressed?

“It all seems to be motivated by a desire to protect the Saudis,” says Sean Carter, a partner in the Philadelphia law firm of Cozen O’Connor. (He is the lead litigator in a lawsuit brought by 9/11 families and insurers that argues that Saudi government employees supported the hijackers, while Saudi-backed charities funded terrorists.)

Indeed, protecting the Saudis has been a bipartisan exercise ever since 9/11.

The Bush administration, which had close ties to the Saudi royal family, classified the 28 pages. Of course, the United States was far more dependent on Saudi oil in 2003 than at present. And then there were, and still are, all those lucrative weapons sales to Riyadh.

But the Obama administration still hasn’t released the 28 pages after nearly two years of review. An impatient Senate just unanimously passed a bill that would let 9/11 families sue Saudi Arabia for any role in the plot. But the White House has threatened to veto the legislation.

Clearly President Barack Obama doesn’t want to worsen his touchy relationship with the monarchy, which is finally sharing intelligence information with America. But with oil prices low and the Islamist terrorist threat high, this excuse won’t wash.

Nor is CIA Director John Brennan’s case against releasing the material convincing. Just two days after the White House said a security review of the pages would be finished by June, Brennan nixed the idea on NBC’s Meet the Press. He said the information in the 28 pages wasn’t vetted or corroborated. He added that it would be “very, very inaccurate” to point to Saudi involvement.

Meantime, the Saudis point to a passage in the report of the 9/11 Commission (published two years after the 2002 congressional inquiry) that they insist exonerates them. The passage states: “We have found no evidence that the Saudi government as an institution or senior Saudi officials individually funded the organization.”

But, as Carter notes, that passage is very carefully worded. It leaves open the possibility that lower-level Saudi officials helped the hijackers carry out the attacks while funding the al-Qaida network.

That point was made bluntly last week, in an interview in the Guardian, by former Navy Secretary John Lehman, a Republican member of the 9/11 Commission.

Lehman said: “There was an awful lot of participation by Saudi individuals in supporting the hijackers, and some of those people worked in the Saudi government. Our report should never have been read as an exoneration of Saudi Arabia.” He added that he didn’t believe the Saudi royal family or senior civilian leadership had any role in supporting the 9/11 plot.

But given the bipartisan reluctance to pursue the Saudi issue, do we really know that?

Here’s some of what we apparently do know, according to an April segment on “60 Minutes” that interviewed several members of the congressional inquiry, all of whom want the pages released: Two weeks after two of the Saudi hijackers got to Los Angeles, a Saudi national, Omar al-Bayoumi, who is listed in FBI files before 9/11 as a Saudi agent, helped them move to San Diego, get housing, and enroll in flight school.

Bayoumi’s spiritual adviser, ensconced at the Saudi consulate in Los Angeles, was Fahad al-Thumairy, an official of the Ministry of Islamic Affairs (which was known to support Islamic extremists). Thumairy was deported in 2002 because of suspected terrorist links.

Bayoumi also had links with an imam at a San Diego mosque — the infamous Anwar al-Awlaki — later a key al-Qaida figure in Yemen who was taken out by a U.S. missile.

There is reportedly more detail in the 28 pages, but one can already smell the smoke.

If this information is unvetted, why wasn’t it further investigated by the 9/11 Commission? And can we really believe that no senior Saudis were aware of Bayoumi’s actions? (It all reminds me of the steadfast Pakistani government denials that any official knew Osama bin Laden lived for years near a major military base in Abbottabad.)

Relations with the Saudis do still matter. But how can there be any solid alliance with a kingdom that spends billions of dollars to export an intolerant brand of Islam — and whose religious charities may still be funding bad guys?

Certainly, such an alliance is based on quicksand until we have clarified whether any Saudi official helped destroy the twin towers.

— Trudy Rubin is a columnist for the Philadelphia Inquirer.