"We have to know which targets to attack and how to attack them," said one, speaking on condition of anonymity.
The flights, which have been going on for weeks, are being launched from sites in Afghanistan and Iraq and are part of Bush administration attempts collect badly needed intelligence on Iran's possible nuclear weapons development sites, these sources said, speaking on condition of strict anonymity.
"These Iranian air defense positions are not just being observed, they're being 'templated,'" an administration official said, explaining that the flights are part of a U.S. effort to develop "an electronic order of battle for Iran" in case of actual conflict.
However, a Pentagon spokesman told UPI he was unaware of any such actions.
"We are not aware of any incursions into Iranian air space," said Cdr. Nick Balice, chief of media at the U.S. Central Command.
In the event of an actual clash, Iran's air defense radars would be targeted for destruction by air-fired U.S. anti-radiation or ARM missiles, he said.
A serving U.S. intelligence official added: "You need to know what proportion of your initial air strikes are going to have to be devoted to air defense suppression."
A CentCom official told United Press International that in the event of a real military strikes, U.S. military forces would be using jamming, deception, and physical attack of Iran's sensors and its Command, Control and Intelligence (C3 systems).
He also made clear that that this entails "advance, detailed knowledge of the enemy's electronic order of battle and careful preplanning."
Ellen Laipson, president and CEO of the Henry L. Stimson Center and former CIA Middle East expert, said of the flights, "They are not necessarily an act of war in themselves, unless they are perceived as being so by the country that is being overflown."
Laipson explained: "It's not unusual for countries to test each other's air defenses from time to time, to do a little probing -- but it can be dangerous if the target country believes that such flights could mean an imminent attack."
She said her concern was that Iran "will not only turn on its air defense radars but use them to fire missiles at U.S. aircraft," an act which would "greatly increase tensions" between the two countries.
The air reconnaissance is taking place in conjunction with other intelligence collection efforts, U.S. government officials said.
To collect badly needed intelligence on the ground about Iran's alleged nuclear program, the United States is depending heavily on Israeli-trained teams of Kurds in northern Iraq and on U.S.-trained teams of former Iranian exiles in the south to gather the intelligence needed for possible strikes against Iran's 13 or more suspected nuclear sites, according to serving and retired U.S. intelligence officials.
Both groups are doing cross border incursions into Iran, some in conjunction with U.S. Special Forces, these sources said.
They claimed the Kurds operating from Kurdistan, in areas they control. The second group, working from the south, is the Mujahedeen-e Khalq, listed by the State Department as a terrorist group, operating from southern Iraq, these sources said.
The use of the MEK for U.S.-intelligence-gathering missions strikes some former U.S. intelligence officials as bizarre. The State Department's annual publication, "Patterns of Global Terrorism," lists them as a terrorist organization.
According to the State Department report, the MEK were allies with Iraqi dictator Saddam Hussein in fighting Iran and, in addition, "assisted Saddam in "suppressing opposition within Iraq, and performed internal security for the Iraqi regime."
After the U.S. invasion of Iraq in March 2003, U.S. forces seized and destroyed MEK munitions and weapons, and about 4,000 MEK operatives were "consolidated, detained, disarmed, and screened for any past terrorist acts, the report said.
Shortly afterwards, the Bush administration began to use them in its covert operations against Iran, former senior U.S. intelligence officials said.
"They've been active in the south for some time," said former CIA counterterrorism chief, Vince Cannistraro.
The MEK are said to be currently launching raids from Camp Habib in Basra, but recently Pakistan President Pervez Musharaff granted permission for the MEK to operate from Pakistan's Baluchi area, U.S. officials said.
Asked about the Musharaff decision, Laipson said: "Not a smart move. The last thing he (Musharaff) needs is another batch of hotheads on Pakistani soil."
A former senior Iranian diplomat told United Press International that the Kurds in the Baluchi areas of Pakistan can operate in freedom because the Baluchis "have no love for the mullahs of Iran."
In fact, in the early 1980s, there were massacres of Iranian Revolutionary Guards in the area by Baluchi militants who wish to be independent, he said.
Both covert groups are tasked by the Bush administration with planting sensors or "sniffers" close to suspected Iran nuclear weapons development sites that will enable the Bush administration to monitor the progress on the program and develop targeting data, these sources said.
"There is an urgent need to obtain this information, at least in the minds of administration hawks," an administration official said.
"This looks to be turning into a pretty large-scale covert operation," a former long-time CIA operator in the region told UPI. In addition to the air strikes on allegedly Iranian nuclear weapons sites, the second aim of the operation is to secure the support in Iran of those "who view U.S. policy of hostility towards Iran's clerics with favor," he said.
The United States is also attempting to erect a covert infrastructure in Iran able to support U.S. efforts, this source said. It consists of Israelis and other U.S. assets, using third country passports, who have created a network of front companies that they own and staff. "It's a covert infrastructure for material support," a U.S. administration official said.
The network would be able to move money, weapons and personnel around inside Iran, he said. The covert infrastructure could also provide safe houses and the like, he said.
Cannistraro, who knew of the program, said: "I doubt the quality of these kinds or programs," explaining the United States had set up a similar network just before the hostage-rescue attempt in 1980. "People forget that the Iranians quickly rolled up that entire network after the rescue attempt failed," Cannistraro said.
The administration's fear is that by possessing a nuclear weapon, Iran will gain a new stature and status in the region strengthening its determination to remove the U.S presence from the region and making its hostility seem more credible, U.S. officials said.
There is also the administration's fear that Iran, with Syria's help, will accelerate Palestinian terrorism as Israel withdraws from the Gaza Strip, these sources said.
So the United States, backed by Israel, is deadly earnest about neutralizing Iran's nuclear weapons site. "The administration has determined that there is no diplomatic solution," said John Pike, president of the online think-tank globalsecurity.org.
"Like the Israelis, the Bush administration has decided that forces of sweetness and light won't be running Iran any time soon, and that having atomic ayatollahs is simply not acceptable."
Said Cannistraro of the administration's policy: "Its very, very, very dangerous."