VERY DISTURBING

U.S. forces arriving in Iraq are being singled out for kidnapping by insurgents, according to senior military officers. The insurgents, they say, might make a symbolic spectacle of abducted soldiers or use captives to negotiate the release of Iraqi prisoners.

Military commanders are also concerned about a possible new terrorist tactic to pose as police officers. U.S. officials are worried that Iraqi police -- not just impostors in Iraqi uniforms -- may have been behind the killings of two coalition staffers and their translator, the top American general in Iraq said yesterday.

The warning on kidnapping is being given to Marine Corps and Army ground forces rotating into Iraq. The military officers say the information has come from a number of intelligence discoveries, though they specified only one: a seized letter the Americans say was written by Abu Musab al-Zarqawi, a Jordanian terrorist suspected of al-Qaida ties...

Army and Marine Corps commanders say that arriving troops express concern about the threat of kidnapping, but that, as one officer put it, any anxiety will diminish "once they're inside the country, once they've got their feet on the ground."

"You've got a gun in your hands, and you've got more than enough for a fair fight," the officer said.