The US may be trying to achieve a difficult balance regarding Iran: pushing the Iranians hard enough so they will negotiate over their nuclear program, yet not so hard as to increase tensions in a part of the world that's already aflame.
That's the conclusion some experts draw from the recent US attempt to lay out evidence that officials say links Iran to attacks against US troops in Iraq.
For weeks the White House had promised that it would present proof that Tehran is meddling in Iraq by providing arms and training to Shiite militias. Yet when the presentation came, it was somewhat low-key. It took place in Baghdad, not Washington. It focused almost entirely on a type of dangerous roadside bomb that Iran is allegedly supplying to its Iraqi allies.
Washington "is not claiming this is decisive, and they're not blaming the [Iraqi] insurgency on Iran," says George Perkovich, a nuclear nonproliferation scholar at the Carnegie Endowment for International Peace. "This is part of a bigger diplomatic strategy, which is genuinely designed to try to put more pressure on Iran so it will want to negotiate, and will be more forthcoming when it does."
The presentation last weekend involved three US officials who briefed reporters on the condition they not be identified. They said that since June 2004, more than 170 US troops have been killed by a special type of bomb called an "explosively formed projectile."
These weapons are capable of blowing a hole in a heavily armored M-1 Abrams tank, according to the officials. US intelligence believes the bombs are made in Iran and that they are smuggled into Iraq by rogue elements of the Shiite Mahdi Army.
The smuggling routes pass through the Iranian border city of Meran, Amareh, Iraq, and the southern Iraqi region around Basra, according to the officials.
Officials at the Baghdad briefing claimed these deliveries are sanctioned by the highest levels of the Iranian government. However, on Tuesday the top US uniformed military officer said that he was not sure that Iranian leaders were behind the shipments.
"That does not translate that the Iranian government per se, for sure, is directly involved in doing this," said Gen. Peter Pace, chairman of the Joint Chiefs of Staff in comments to reporters while traveling in Indonesia. "What it does say is that things made in Iran are being used in Iraq to kill coalition soldiers."
Critics of the administration's policies in the region generally were unconvinced by the evidence that Iran is playing a substantial role in the Iraq conflict.
That Iranian weapons are found in Iraq is unsurprising, some said. After all, Iran is next door to a hot war, has longstanding ties with some of the combatants, and fears a collapse of the government of Prime Minister Nouri al-Maliki as much as does the US.
But establishing the complicity of Iranian leaders such as President Mahmoud Ahmadinejad or Ayatollah Ali Khamenei, Iran's supreme leader, is another matter.
"Some of it is true," says Vali Nasr, a professor at the Naval Postgraduate School and author of a new book on the Shiite revival, of the US allegations.
Considering the scale of the violence in Iraq, however, Iranian involvement might be considered something of a sideshow, in military terms, says Mr. Nasr.
"Where do the weapons that bring down the US helicopters come from?" he asks. "Not Iran."
Iranian aid surely is not a decisive issue in Iraq, agrees Mr. Perkovich. Even if Iran did not exist, the violence in Iraq would be much the same as it is today.
Nor are the US allegations part of a plan to justify the administration's refusal to enter into talks with Iran over Iraq's future, according to Perkovich. The recent report of the Iraq Study Group suggested that the White House open talks with Iran and Syria as a way to quell the violence.
Not that the Iranians necessarily want to talk to the US about Iraq.
"The Iranians may not want to work with us on Iraq," says Perkovich. "If they negotiate, they will get pushed to make things better, and they know they don't have too much control there."
Instead, the US presentation of evidence perhaps should be seen as part of the larger effort by Washington to manage its relations with Tehran, especially in light of Iran's apparent intention to press ahead with a uranium- enrichment program.
"This is all about pushing back on the Iranians, shining light on them in ways that can engender debate in Tehran," says Perkovich.
Reportedly, the evidence presented over the weekend represented a pared-down version of a military briefing that details allegations of wider Iranian activities inside Iraq's borders.
Mindful of charges that intelligence about Iraq's alleged weapons of mass destruction was inflated for political reasons prior to the Iraq war, the administration may have decided that a low-key approach was the best way to go.
"We're not getting ready for war in Iran, but what we are doing is we're protecting our own people," said White House spokesman Tony Snow on Monday.