As if the insurgency in Iraq and the fight against terrorism wasn't enough, U.S. diplomats are now struggling with a new threat: menacing "killer" wasps that have infested areas around the State Department's headquarters.

Large numbers of the fearsome looking insects, which can grow to about two inches, are congregating in the vicinity of State's Harry S. Truman building and causing distress to employees, according to an internal memorandum obtained by The Associated Press.

These are 'cicada killer' wasps, which, despite their somewhat alarming appearance and name, are generally not aggressive and do not pose a threat to humans," said the notice, which was distributed on Thursday in a bid to ease fears.

"Almost all of the wasps flying around the nesting areas are males, which typically do not sting unless disturbed during mating," it says. "The female wasps prey on cicadas and are unlikely to bother passers- by unless directly threatened."

The notice, which includes a photo of a typical wasp, points employees who have additional concerns to the Web site of the University of Kentucky entomology department for details about the cicada killers and their mating habits.

However, that Web site is unlikely to calm the diplomats' nerves, inasmuch as it notes that both males and females will attack humans when bothered during mating season which runs through the summer months.