WASHINGTON >> Just hours after it was revealed that U.S. soldiers had burned Qurans seized at an Afghan detention center in late February, Iran secretly ordered its agents operating inside Afghanistan to exploit the anticipated public outrage by trying to instigate violent protests in the capital, Kabul, and across the western part of the country, according to U.S. officials.

For the most part, the efforts by Iranian agents and local surrogates failed to provoke widespread or lasting unrest, the officials said. Yet with NATO governments preparing for possible retaliation by Iran in the event of an Israeli attack on its nuclear facilities, Iran’s willingness and ability to foment violence in Afghanistan and elsewhere has taken on added urgency.

With Iran’s motives and operational intentions a subject of intense interest, U.S. officials have closely studied recent incidents. A mixed picture of Iranian capabilities has emerged, according to interviews with more than a dozen officials across the government, most of whom discussed the risks on the condition of anonymity because their comments were based on intelligence reports.

One U.S. government official described the Iranian Embassy in Kabul as having “a very active” program of anti-American provocation, but it is not clear whether Iran deliberately chose to limit its efforts after the Quran burning or was unable to carry out operations that would have caused more significant harm.

In offering an overall view of the threat from Tehran, Gen. John R. Allen, the senior allied commander in Afghanistan, told Congress in recent public testimony that Iran continued to “fuel the flames of violence” by supporting the Afghan insurgency. “Our sense is that Iran could do more if they chose to,” Allen said. “But they have not, and we watch the activity and the relationships very closely.”

The most visible rioting that U.S. officials say bears Iranian fingerprints occurred in Herat province, along Afghanistan’s western border with Iran. In a melee after the Quran burning, seven people were killed and 65 were wounded, Afghan and U.S. officials said. That violence peaked when a police ammunition truck was hit by gunfire from a rioter and exploded.

Iran has denied any government-backed effort to foment unrest in Afghanistan, but U.S. officials see a pattern of malign meddling designed to increase Iran’s influence across the Middle East and South Asia. Iran appears to have increased its political outreach and arms shipments to rebels and other political figures in Yemen, and it is arming and advising the embattled government of President Bashar Assad of Syria.

Those activities also reflect a broader campaign that includes what U.S. officials say was a failed plot to assassinate the Saudi ambassador to the United States in October, and what appears to have been a coordinated effort by Iran to attack Israeli diplomats in India and Georgia earlier this year. Iran has denied any role in the attacks, which caused several injuries but did not kill anyone.

But the absence of a sustained record of clear success in these plots, including Iran’s suspected role in the riots in Herat and in similar disturbances in Kabul, has stirred a vigorous debate among Western intelligence agencies about the country’s surprisingly low level of professionalism, and about whether Iran maintains the ability to carry out effective strikes against rivals beyond its traditional networks in the Middle East.

“The attacks failed, so clearly there are kinks in Iran’s planning and tradecraft,” one U.S. official said.

Western intelligence analysts emphasize that Iran can still tap the formidable global resources of Hezbollah, the Lebanese Shiite militant group. And some U.S. officials are wary of viewing the recent plots as a sign of Iran’s diminishing ability to instigate violence.

“They’re learning from each of these incidents and becoming more dangerous,” Rep. Mike Rogers, R-Mich., who leads the House Intelligence Committee, said in a telephone interview.

Rogers said that Iran’s intelligence service and the Quds Force, an elite international operations unit within the country’s Islamic Revolutionary Guards Corps, appeared to be competing with each other for influence, increasing the risk to the West.

“The intent is not devastating operations, but raising the temperature to create deterrence,” said Vali Nasr, a former State Department official who worked on these issues and was recently named dean of the Johns Hopkins School of Advanced International Studies. “Amateurs are tougher to detect and catch. It caught our surveillance off guard. We were looking for pros. They went below the radar.”

The plots have also prompted U.S. and other Western intelligence agencies to renew their focus on state-sponsored terrorism after a decade dominated by al-Qaida, its regional affiliates and other shadowy terrorist networks.

U.S. officials say they never took their eye off state-sponsored threats, but rising tensions with Iran have caused these organizations to re-emerge in the public eye as a concern. In Afghanistan, according to U.S. officials, Iranian assistance to militants and insurgents is limited to training, money, explosive material, small arms, rockets and mortars.

But Allen, in two days of testimony before Congress, disclosed that NATO forces were watching for an infusion of more-advanced weapons — in particular a high-powered roadway bomb called an explosively formed projectile, or EFP, which can pierce U.S. armored vehicles. These bombs proved their deadly effectiveness when Iran funneled them to Shiite militants during the height of the sectarian violence in Iraq.

“So we’re going to keep a very close eye on those signature weapons,” Allen said, “because we think that that will be an indicator of Iran’s desire to up the ante, in which case we’ll have to take other actions.”

Iran has long faced a quandary in shaping an Afghan policy. It has wanted to target the Americans fighting in Afghanistan, and the best mechanism for doing that is the Taliban insurgency. But at the same time, Iran has little interest in the return of a Taliban regime. When they were in power, the Taliban often persecuted the Hazara minority, who, like most Iranians, are Shiite, and whom Iran supports.

What Iran has pursued more relentlessly is an effort to pull the Afghan government away from the Americans, a strategy that has included payments to promote Iran’s interests with President Hamid Karzai.

One U.S. intelligence analyst noted that Iran had long supported Afghan minorities, both Shiite and Sunni, and had built a network of support among Hazaras, Uzbeks and Tajiks.

Iran has exercised other means of “soft power,” the analyst said, opening schools in western Afghanistan to help extend its influence. The Iranians have also opened schools in Kabul and have largely financed a university attached to a large new Shiite mosque.

Iran is thought to back at least eight newspapers in Kabul and a number of television and radio stations, according to Afghan and Western officials. The Iranian-backed news organs kept fanning anti-American sentiment for days after the burning of the Qurans.