Updated

Bush administration officials are concerned about a spectacular attack or series of attacks designed to coincide with the September release of a critical progress report in Iraq, a senior administration official confirmed to FOX News on Sunday.

The official, however, would not go into any specifics about an upcoming National Intelligence Estimate that reportedly suggests Iraq is in for more violence despite political strides made by that country's parliament and recent military successes on the ground.

A U.S. official in Baghdad said the military has been warning since mid-June that terrorists may try a spectacular attack. Despite progress made in the surge, Al Qaeda in Iraq has the capability today of launching a large-scale attack on a soft target like a market, for example, the official said.

The September report by Gen. David Petraeus, the top U.S. commander in Iraq, and U.S. Ambassador to Iraq Ryan Crocker, is expected to list military and political benchmarks achieved to date, and has become its own benchmark for supporters and opponents to justify staying in or leaving Iraq.

A Politico.com report out late Saturday revealed that some administration officials are concerned that before the report is complete, Al Qaeda will try to undertake some attack similar to the Tet Offensive of 1968. In that attack, Vietnamese Communists were able to coordinate a surprise volley of assaults that produced a psychological victory there, leading President Lyndon Johnson and Washington newsmakers to re-evaluate U.S. war policy.

Click here to read the Politico.com story.

According to Politico.com, the NIE is likely to offer some positive assessments — primarily about the increasing cooperation of Iraqis who are tipping off activities of bad actors, a drop-off in attacks from 30 to 40 per day in some areas to fewer than one per day and a reduction in sectarian violence in some areas.

But the draft also is to depict Iraq generally as a mess and will warn that Syria continues to be unhelpful while the threat from Iran increases, Politico.com reported.

"The NIE, an update to the one from Feb. 2, will likely offer a picture of the current successes as well as the remaining challenges we face in Iraq, and, like the previous NIE on Iraq, the consequences of pursuing different courses of action," National Security Council spokesman Gordon Johndroe told FOX News.

The NIE — a collective assessment of the 16 U.S. intelligence agencies used to predict future activities — could come by week's end, a U.S. official told FOX News, though a date has not been publicly announced. Portions of the report are often declassified.

A senior U.S. official confirmed excerpts of the draft report to FOX News, but warned about accepting the details whole-cloth.

"I'd be cautious about leaked snippets from a draft report. The last NIE painted a mixed picture, this one likely will too," the official said.

A U.S. intelligence official said he couldn't talk about "an intelligence community product that is still in the works. Nevertheless, an NIE is a comprehensive assessment — a long term forecast."

The intelligence official added, "Policy makers are always receiving the most up to date intelligence, but an NIE looks to the future."

FOX News' Bret Baier and Mike Emanuel contributed to this report.