Saudi Arabia and Libya, both considered allies by the United States in its fight against terrorism, were the source of about 60 percent of the foreign fighters who came to Iraq in the past year to serve as suicide bombers or to facilitate other attacks, according to senior American military officials.

The data come largely from a trove of documents and computers discovered in September, when American forces raided a tent camp in the desert near Sinjar, close to the Syrian border. The raid’s target was an insurgent cell believed to be responsible for smuggling the vast majority of foreign fighters into Iraq.

The most significant discovery was a collection of biographical sketches that listed hometowns and other details for more than 700 fighters brought into Iraq since August 2006.

The records also underscore how the insurgency in Iraq remains both overwhelmingly Iraqi and Sunni. American officials now estimate that the flow of foreign fighters was 80 to 110 per month during the first half of this year and about 60 per month during the summer. The numbers fell sharply in October to no more than 40, partly as a result of the Sinjar raid, the American officials say.