The most immediate threat Iran poses to American national security isn't its nuclear (weapons) program. It's the safe haven Tehran is giving al Qaeda terrorists, who are planning and directing jihad across the globe.

If the United States and its allies in the War on Terror don't take firm action against Iranian support to al Qaeda, the price in blood and treasure attributable to Osama bin Laden's killers - in Iraq and elsewhere - will continue to soar.

Shockingly, it's been long forgotten that Iran became home to some of al Qaeda's most wanted after the fall 2001 invasion of Afghanistan. Tehran admitted as much, claiming that al Qaeda operatives were under "house arrest" and would be tried.

Of course, nothing of the sort happened . . .

So al Qaeda "refugees" from Egypt, Saudi Arabia, Uzbekistan, North Africa and Europe - including senior military commander Saif al Adel, three of Osama's sons and spokesman Sulaiman Abu Ghaith - now operate freely from Iran.

In fact, just last week, the German monthly magazine Cicero, citing Western intelligence sources, claimed that as many as 25 al Qaeda thugs are living in Iran under the protection of the Iranian Revolutionary Guard Corps (IRGC).

Cicero cites a "top-ranking" Western intelligence official saying, "This is not incarceration or house arrest. They [al Qaeda members] can move around as they please." The IRGC even provides logistics help and training to al Qaeda.

Cicero doesn't mention which al Qaeda operations Iran is supporting, but there's little doubt that Tehran is aiding the terror in Iraq, where there are more and more Iranian "fingerprints" on insurgent/terrorist attacks.

Iran and al Qaeda have been tight for some time. The 9/11 Commission said that al Qaeda passed freely though Iran before 9/11, including at least eight of the 14 "muscle" hijackers that commandeered the four ill-fated planes. After the USS Cole bombing in 2000, Iranian officials approached al Qaeda to propose a partnership for future anti-U.S. attacks. (Osama nixed the offer for fear of alienating Saudi supporters.)

Al Qaeda also collaborated with Iran in the 1996 bombing of the Khobar Towers in Saudi Arabia. And U.S. intercepts caught al Qaeda operatives in Iran communicating with terrorists in Saudi Arabia before the 2003 attacks there.

And, though conventional wisdom has bin Laden somewhere along the Afghan-Pakistani border, there have also been rumors that he and his deputy, Ayman al-Zawahiri, are under Iran's protection.

Of course, Iran and al Qaeda aren't natural allies. Iran is Persian/Shia, while al Qaeda is Arab/Sunni. But, for the moment, Iran and al Qaeda seem to be looking beyond this and toward a common goal - global Islamic rule and American failure in Iraq.

Getting Tehran to cough up Saif al Adel, al Qaeda's No. 3, would be a major coup. The former Egyptian Special Forces colonel was involved in attacking U.S. forces in Mogadishu (1993) and the U.S. embassies in Kenya/Tanzania (1998). He was also a player in the Cole assault, trained 9/11 hijackers, orchestrated Saudi attacks and acts as an al Qaeda-Hezbollah liaison. He's surely involved in supporting Abu Musab al-Zarqawi's thugs in Iraq.

And not addressing the Iran-al Qaeda axis could allow Iran to become al Qaeda's "new Afghanistan" - a base where Osama's henchmen could raise funds, recruit/train new footsoldiers and plan/direct attacks.

Repeated calls for Iran to turn over al Qaeda members to their countries of origin have gone nowhere. It's time to stop giving Tehran a pass.

Tough, multilateral economic sanctions against Iran are long overdue. Iran's economy has been on the skids for a while; Tehran would feel the pain if the United Nations - or simply its major trading partners, such as Germany, France and Italy - put the squeeze on.

The sound of Tehran's high-pitched squeals whenever economic sanctions are even mentioned - usually over its nuclear (weapons) program - seems to indicate that these measures are something the mullahs would rather avoid.

There's no guarantee that sanctions will get Tehran to swear off its terrorist ways. But, because Iran's economy is so centralized, trade gives the mullahs pocket change to cause trouble at home and across the globe.

So while a nuclear-armed Iran is a serious - but future - threat that has a (slim) chance of a diplomatic solution, the Iranian-al Qaeda terrorist threat is here and now, making the time for action - not negotiations - long past.

Peter Brookes is a Heritage Foundation senior fellow. His book, "A Devil's Triangle: Terrorism, WMD and Rogue States," is just out