The conservative magazine Human Events noted the number of al-Qaida fighters in Iraq had approached some 20,000, but anonymous sources in the U.S. intelligence community put the current total at less than 5,000.

"Al Qaida in Iraq's overall strength is down by well over half in the last year," sources say.

The source said that al-Qaida leadership in Pakistan and Afghanistan recognize their efforts in Iraq are dwindling, but still maintain their ability to upset the fragile security situation as a spate of suicide bombings have rocked the war-torn country in recent weeks.

U.S. intelligence officials told the magazine they had intercepted several e-mail and cell phone conversations suggesting al-Qaida agents are on the run as several safe havens are coming under increased attacks.

Eliminating al-Qaida from Iraq would be a significant boost to the broader U.S.-led global counter-terrorism campaign, the report said. Some analysts, however, caution al-Qaida in Iraq is restructuring its hierarchy and strategy as the number of U.S. troops continues to decline.

Meanwhile, a statement from the reported head of al-Qaida in Iraq, Abu Omar al-Baghdadi, issued a 37-minute audio message Sept. 24 calling on former fighters to join forces once again in Iraq.