The point of this week's deadly bomb attacks in Iraq may be to foment factional unrest, which could pit Shiite Muslims against Sunnis and even escalate into bitter civil war.
So far Iraqi Shiites don't appear to be blaming Sunnis as a whole for the explosions that darkened their annual festival of Ashura. Initial anger appeared directed at Americans, who Shiite leaders charged with failure to provide necessary security.
But US officials and experts suspect the suicide bombings were the handiwork of Abu Musab al-Zarqawi, a Jordanian Sunni linked to Al Qaeda who may be striving to jumpstart sectarian strife. At the least, fear of further attack could lead Shiites to expand their religious militia, further dividing the country even as it approaches the June 30 deadline for resumption of Iraqi sovereignty.
"These [attackers], whoever they are ... they're just trying to create factional, religious, intercommunal strife to undermine what the US is doing," says a former US intelligence official who works in the region.
US authorities had long worried about possible turmoil during this year's Ashura, a holy day suppressed for 25 years during the Saddam Hussein regime. But even they appeared taken aback by the toll of the suicide attacks on Shiite celebrants. Tuesday was the deadliest day in Iraq since the end of major military operations 11 months ago.
Both the Iraqi Governing Council and US administrators were quick to proclaim Zarqawi the most likely perpetrator. Brig. Gen. Mark Kimmit, a spokesman for the US military in the region, called him "the most likely suspect."
The US produced no hard evidence linking Zarqawi to the attacks, however. On Wednesday, a letter purported to come from Osama bin Laden's Al Qaeda network denied any role in the bombings. The "massacre" was instead carried out by US troops, charged the letter, which was published in the London-based al-Quds al-Arabi newspaper.
The reason Zarqawi could be behind the attacks, say US officials and experts, is because they reflect his purported strategy. In January, the US said that it had found a copy of a letter from the Jordanian militant to his Al Qaeda superiors in a computer in Iraq. The letter's text urges sectarian and factional killings all too clearly.
It calls Iraqi Shiites "the spying enemy and the penetrating venom." Targeting them will provoke retaliation against Iraqi Sunnis, says the letter, "awakening" the latter and plunging the nation into instability and war.
"Zero hour will [come] four months or so before the promised government is formed [on June 30]," concludes the letter.
Not all experts accept the Zarqawi letter as authentic. Some suspect it to be disinformation spread by either Al Qaeda or the Americans themselves.
But others say that the attempt to create sectarian strife, which it describes, is clearly happening. Previous bombs have already struck at the Kurdish leadership in the north of the country, and Shiite clerics.
Tuesday's attacks are "the latest and the worst, but not the first of a series of really worrisome operations," says Jim Walsh, an international security expert at Harvard University's John F. Kennedy School of Government.
Zarqawi might be pursuing his divide-and-conquer strategy whether it has Osama bin Laden's backing or not. His letter seemed a plea to a superior leader for support, and he would probably like to be seen as someone sanctioned by Al Qaeda's top leaders. But in many ways he is an independent actor, say US terrorism experts.
"He is basically setting himself up as a competitor of bin Laden," says Bruce Hoffman, an analyst at the RAND Corporation.
At this point, it's difficult to speculate whether the attacks will succeed in splitting Iraq along factional lines. If Shiites see a Sunni-backed insurgency as being the cause of disaster on one of their holiest of days, it will strain cooperation between factions, at the very least.
But so far that does not seem to be happening.
"Everybody seems to be preaching moderation and caution - at least for now," says the former US intelligence official.
It's even possible the attacks could drive factions together. Iraqi Shiites know their anguish was caused by foreign jihadists, in this analysis, and thus will encourage the Americans to continue efforts to crush insurgents. Iraqi Sunnis won't want to start a civil war they would probably lose, being a minority in their country, and will find accommodation to be their only option.
Of course, general lawlessness could yet upset US transition plans. The Shiites, Sunnis, and Kurds, in essence, all possess their own militias. If the different factions believe they must rely on themselves for security, the private armies could grow. With June 30 approaching, Iraq might come to resemble the Wild West.
"All you need is a spark at that point," says Mr. Walsh.