国际英语新闻：Gates says war documents leak dangerous to troops, allies

Gates said he has asked the Federal Bureau of Investigation for assistance, promising to aggressively investigate the leak's source. The investigation is being handled by the Army's criminal investigation branch.

Pentagon spokesman Geoff Morrell earlier said Bradley Manning, a 22-year-old private charged in an earlier leak to WikiLeaks, was named a "person of interest" in the new investigation.

Gates also said the military will be tightening procedures that safeguard classified information. The Pentagon has started clamping down on access in the field to sensitive information to reduce the risk of another leak, he said.