The smooth blacktop roads and 24-hour electricity of Herat set this Afghan commercial capital apart as a model of stability in a country still struggling to get on its feet. Much of the wealth in this western city, with its tree-lined streets and handsome shops, is credited to the largesse of Iran.
The Shiite republic, one of Afghanistan's greatest trading partners, has a visible hand here, building roads and schools, and keeping shops afloat with electricity and goods. What's more, these projects represent only a fraction of the $204 million Iran has spent in aid, ranking it among the top donors to post-conflict Afghanistan.
Even though the US and Iran are locked in an international struggle over Iran's alleged pursuit of nuclear weapons, the long-time foes have worked together well in Afghanistan, a place where they have common ground. Pushing Iran against the wall through sanctions or war could deal a setback to the recovery here, the first battlefield in the war on terror, some observers say.
"The disagreements we have with the international community do not have a place in Afghanistan," says Mohammad Reza Bahrami, Iran's Ambassador to Afghanistan. "Our understanding for Afghanistan is that it can be a good model for cooperation among the international community."
Iranian influence is certainly nothing new in Afghanistan. The two countries share centuries of history, thousands of miles of porous borders, and a common language. Nearly 2,000 people commute across the border every day.
But as tensions rise between Tehran and Washington, some speculate that Iran could use its leverage in Afghanistan to cause problems for the US.
"They do have the capacity to cause trouble here. If they were to perceive that the government is siding with the West ... or they felt that the US military based in Afghanistan could be damaging to the internal situation in Iran ... we could expect problems here," cautioned one Western diplomat, who spoke on the condition of anonymity, citing the sensitivity of the issue.
Cement is a popular example of Iran's oversized influence. Iran once enjoyed a virtual monopoly on cement in Afghanistan, but it recently stopped exporting here, opting for Iraq instead. Prices nearly doubled according to local sources. For many Afghans, the incident exposed Iran's capability to disrupt reconstruction with the flip of a switch.
"If Iran decides to stop exporting goods, it can create a big problem for us," says Alhaj Qulam Qader Akbar, the head of Herat's Chamber of Commerce. "A lot of projects have been suspended because of the price [of cement] going up."
Such disruptive powers are not limited to the market, some say. Journalists talk of Iran's growing involvement in terrorist attacks here. Rumors also abound that Iran's Revolutionary Guard is secretly camped out in Herat.
Syed Ahmed Ansari, a police chief for Shindad, a town in Herat Province, told the Associated Press in February: "From Iran they are bringing explosive material to Afghanistan. They don't want Afghanistan to be at peace because they are at war with the United States."
So far, though, there is no direct evidence of such meddling, and Iran has never been directly implicated in any attacks. "We don't have evidence of that, but that is something we hear. If we want to comment on something, we should have evidence," says Gen. Ayub Salangi, Herat's chief of police.
Mr. Bahrimi, the Iranian ambassador, insists his country's role in Iran has always been a positive one. But he suggests that action taken against Iran could change that role.
"If new circumstances are imposed on us, in proportion to these circumstances, we'll make up our mind," he says, adding, "If [the Americans] control their behavior in Afghanistan, there isn't any reason for concern."
Even in the US, those closely watching Iran are hard pressed to find evidence of misconduct in Afghanistan. Instead, some have found themselves admitting that Iran, despite its activities elsewhere, has proved to be a good neighbor here.
Such was the case during a March congressional hearing on progress in Afghanistan. A panel of experts working on Afghanistan unanimously highlighted Iran's contribution to stability.
"I do not believe Iran is a major, negative player in Afghanistan," Seth Jones of the Rand Corporation told the panel. "If anything, the Iranian government's role in relationship with the Afghan government is actually fairly decent."
Barnett Rubin, a professor at New York University, went a step further, saying: "[W]e should be wary of anyone who is trying to sell intelligence or reports that Iran is trying to destabilize Afghanistan. It is not."
In fact, such are the contributions of Iran here that forcing it to pull out, either through sanctions or war, could hamper reconstruction, particularly by destabilizing the economy, many speculate.
"The tensions that Iran has with the international community are a deep cause of concern for us. If there are sanctions, or other means of exerting pressure, it will have its implications on Afghanistan. And that's the last thing we need," says Naveed Ahmad Moez, spokesperson for the foreign ministry.
Iran's support of the Karzai government stems in part from its antipathy toward the Taliban regime, which killed nine Iranian diplomats in 1998. Tehran supported the Northern Alliance and the US in ousting them.
Many say it's simply not in Iran's interest to make waves. Cross-border business is booming and the western border is stable. But there are those who say the US would be foolish to completely rule it out.
"The Americans should be concerned about Iranian influence," says Najibullah Fahim, professor of political science at Kabul University. "You know that Iran is hostile to America and will create enmity towards Americans here."
Sen. William Delahunt (D) of Massachusetts, who attended the March congressional hearing, seemed to think likewise. But when he pressed Maureen Quinn from the State Department, her retort was short but to the point.
"Iran participated in the London conference," she said, referring to an international donor meeting held in January. "They have contributed to road construction, electricity."