The June 13 attack on an American military convoy in Afghanistan—the third suicide bombing there in recent weeks—suggests that an alarming development may be under way: the importation of insurgent techniques from Iraq to Afghanistan.

The attack, which injured four (at least one of them critically), follows bombings in a Kabul guesthouse, which killed three, and against a Kandahar mosque, which left 19 dead and 52 injured. Until last month, these tactics were rare in Afghanistan: only five suicide attacks have been reported since the fall of the Taliban three and a half years ago, none of which targeted civilians. The bombings, part of a wave of attacks that include assassinations and kidnappings, suggest that insurgents are borrowing tactics from Iraq. The spread of Iraq's problems to Afghanistan would be devastating to stability there and throughout the region.

It's worth recalling that suicide bombings were rare in Iraq immediately after the invasion. There were several scattered suicide attacks against soldiers in the first few months, but the tactic lacked support. Then, five months after the invasion, a massive blast leveled the UN headquarters in Baghdad, ushering in a new phase of the war. The radical element of the insurgency had tasted blood.

Today, Iraq's suicide attacks are tragically common. The escalating use of suicide bombs has pushed U.S. fatalities to 1,674, and Iraqi officials estimate that 12,000 civilians have been killed over the past eighteen months-an average of 20 Iraqi civilians killed every day. The Los Angeles Times reported that suicide bombings "outpaced car bombings almost 2-to-1 in May," with "a staggering 90 attacks accounting for most of last month's 750 deaths." In April alone there were 69 suicide attacks, "more than in the entire year preceding the June 28, 2004, hand-over of sovereignty."

The diffusion of extreme tactics in insurgency is difficult to predict. It is perhaps surprising that suicide bombs have been so rare in Afghanistan, since the tactic would seem well suited the Taliban's relatively unskilled but highly motivated insurgents. But suicide bombings, like other tactics, are spread by importation and demonstration. In Iraq, the rise in suicide tactics correlates with the influx of foreign jihadists, who used these tactics in Chechnya and the Palestinian territories. (According to the Pentagon, foreign jihadists, comprise only ten percent of insurgents in Iraq but account for nearly all the suicide bombs targeting Iraqi civilians.)

According to a recent Washington Post- ABC News poll, a majority of Americans now believe the war against Iraq has made America less safe. The reasons frequently cited are the strains on the military, the massive expenses, the surge in anti-Americanism, the undermining of traditional alliances, and the diversion from more pressing threats in Iran and North Korea. But there's another reason as well, one that will persist for many years: the war in Iraq has demonstrated how a dedicated insurgency, through targeted brutality, can stalemate a technologically and numerically superior American force. In effect, Iraq has updated, and broadcast globally, the lessons of Vietnam and Beirut to a new generation of potential adversaries.

Afghanistan has been held out as a success story in contrast to Iraq's persistent violence, but victory remains far from certain. After a winter lull, Afghanistan has been just as dangerous for U.S. troops: Pentagon figures show that since early March, American deaths in Afghanistan are 1.6 per 1000 troops deployed, compared to 0.9 per 1,000 in Iraq over the same period. "It's not supposed to be like that here," said Capt. Mike Adamski, quoted in a June 4 New York Times article after a firefight with the Taliban in May. "It's the hardest fight I saw, even after Iraq."

The neo-Taliban, dwindling in numbers and threatened by an armistice agreement that could integrate its moderate members into the government, has little to lose. Their collaboration with foreign jihadists, whom the government blames for the three suicide bombings (the account remains in dispute), could further radicalize the movement. Like the Iraqi insurgency, the Taliban realize they cannot hold ground but can wreak political havoc. The strategy in both cases is similar: sustain operations, cause casualties, undermine the government's credibility, and outlast the international forces.

Three suicide bombings and a rash of Iraq-style assassinations and kidnappings do not themselves constitute a trend. But the United States cannot wait for the problem to become manifest. Proactive diplomacy must engage Afghan authorities, clerics, and regional and tribal leaders to disavow suicide bombing as a foreign and terrorist tactic that has no place in Afghanistan. It may still be possible to split off moderate Taliban supporters from the extremists and foreign jihadists responsible for the latest attacks.

The costs of failure are great. If Iraqi tactics are imported to Afghanistan it could ignite a bloody second front against an American army that is stretched perilously thin. That would be one more cost of the war in Iraq that no one calculated.

Carl Robichaud, a program officer at The Century Foundation, is editor of Afghanistan Watch and co-author of Rule of Law: The Missing Priority, which examines post-conflict organized criminality in Bosnia, Kosovo, Afghanistan, and Iraq.