Years ago, one of the arguments I made in favor of Bill Clinton’s intervention in Kosovo was that, if the U.S. hadn’t acted, Islamist groups would have stepped forward to aid the insurgency and Kosovo would have become a breeding ground for jihadist terrorism. It turns out that danger was only temporarily averted by U.S. intervention.

In the New York Times, correspondent Carlotta Gall has an eye-opening dispatch from Pristina detailing how extensive support for terrorism has become in modern Kosovo. “Over the last two years,” she wrote, “the police have identified 314 Kosovars — including two suicide bombers, 44 women and 28 children — who have gone abroad to join the Islamic State, the highest number per capita in Europe.”

What accounts for this surge of extremism? Gall points the finger of blame at America’s allies in the Persian Gulf region, particularly Saudi Arabia. She wrote: “They were radicalized and recruited, Kosovo investigators say, by a corps of extremist clerics and secretive associations funded by Saudi Arabia and other conservative Arab Gulf states using an obscure, labyrinthine network of donations from charities, private individuals, and government ministries… Kosovo now has over 800 mosques, 240 of them built since the war and blamed for helping indoctrinate a new generation in Wahhabism.”

The good news is that Kosovo is still largely pro-American (it is home to Bill Clinton Boulevard!) and still has a moderate Muslim government that is intent on fighting extremism. “After two years of investigations,” Gall notes, “the police have charged 67 people, arrested 14 imams and shut down 19 Muslim organizations for acting against the Constitution, inciting hatred and recruiting for terrorism.”

I still believe the situation would have been far worse if the U.S. had stood aside and allowed a civil war to rage in Kosovo indefinitely. We’ve seen in Syria what that leads to. Nevertheless, what the Saudis and other Gulf Arabs are doing in Kosovo — and far beyond — is deeply disturbing.

Saudi Arabia, in particular, has spent decades and countless billions of dollars spreading its fundamentalist version of Islam to every corner of the world. Its petrodollars have allowed fundamentalist preachers to edge out more moderate local Islamic clerics from Africa to America. In the process, Saudi-funded mosques and madrassas have served as a breeding ground for countless terrorists — including some who have ultimately wound up targeting the Kingdom itself.

Since 2001, Saudi Arabia and other Gulf Arab states have done more to crack down on outright financing of terrorist groups. Their citizens continue to donate funds to the likes of al-Qaeda and ISIS but in smaller amounts than before and without the de facto state sanction that such activities once enjoyed. But in spite of importuning from the U.S. and allies such as Germany, Saudi Arabia has not, as far as I can tell, made as much progress in decreasing its support for mosques and madrassas abroad preaching doctrines of hatred. This is part of the de facto deal the House of Saud has reached with its own clerical establishment: The Wahhabi clerics support the Saudi royal family and overlook its sins and hypocrisies and in return the royals support fundamentalism at home and abroad.

I still believe that Iran is a greater national security threat to the U.S., because it is a revolutionary state explicitly committed to a “Death to America” doctrine, whereas Saudi Arabia is fundamentally a pro-American, status quo power. But the U.S. cannot afford to overlook Saudi support for Wahhabism around the world because it radicalizes so many Muslims who become terrorists.

There is no obvious or easy way to wean the Saudis away from their proselytizing in favor of Wahhabism. But the U.S. would have a stronger case to make if it is showed that it is truly committed to Saudi security by fighting the menace that is the new Persian Empire — rather than trying to make deals with Iran that legitimize its nuclear program and its expansionism, and thereby raising alarms in Riyadh. In return for a greater commitment to Saudi security, the U.S. could reasonably demand of the royal family that they decrease not only funding for terrorism — where significant progress has already been made — but also for Wahhabism in general, which remains an area where there is still much room for progress.

The U.S. needs to apply similar pressure to other Gulf Arab Allies. In fact, Carlotta Gall noted that “in recent years, Saudi Arabia appears to have reduced its aid to Kosovo. Kosovo Central Bank figures show grants from Saudi Arabia averaging €100,000 a year for the past five years.” Unfortunately, the slack has been picked up by the other Gulf States: “It is now money from Kuwait, Qatar, and the United Arab Emirates — which each average approximately €1 million a year — that propagates the same hardline version of Islam.”