WASHINGTON — The first shot in the coming subpoena wars between congressional Democrats and the Bush administration likely will be fired in January by Senator Levin, a Democrat of Michigan.

The Senate Armed Services Committee’s Democratic staff, soon to be in the majority, is already preparing to ask the Pentagon for documents related to analysis in the lead-up to the Iraq war from the offices reporting to a former undersecretary of defense for policy, Douglas Feith.

At issue so far are some 58 documents Mr. Levin requested as early as 2004 that relate to how the Defense Department’s Office of Special Plans may have deviated from the CIA in its view of links between Al Qaeda and Iraq, and whether such deviation constituted pressure on intelligence analysts.

What Mr. Levin intends to do with those documents, should the Pentagon release them, is significant for the president, the ongoing war, and the Democrats.

The initial document request will test an unstated Bush administration policy to presuppose that presidential privilege would shield advice and other internal deliberations in the executive branch, and not just the White House, from congressional subpoena. It is likely, for example, that the privilege defense will be used to attempt to block congressional requests for Justice Department memos that outline interrogation policies for detainees.

While the policy is not mentioned in letters between the Pentagon and Mr. Levin, Defense Department lawyers have conveyed verbally that the 58 documents the senator seeks presumptively fall under presidential privilege.

Should Mr. Levin decide to reopen his inquiry into pre-war intelligence, however, there is a risk that Democrats will be seen as backward-looking. In an interview earlier this month, the head of the centrist Democratic Leadership Council, Al From, said he would caution his party against “relitigating 2003.”

Mr. Levin has been pursuing Mr. Feith and the Office of Special Plans almost since the Iraq war began. According to correspondence between the Pentagon and Mr. Levin obtained byThe New York Sun, the senator has sought every e-mail, staff review, internal legal opinion, and policy draft related to Iraq and Al Qaeda. The former prosecutor ends a June 30, 2004, letter by asking Mr. Feith to provide “all documents and communications from all persons within your Policy organization from September 2001 through April 2003, related to the relationship between Iraq and al Qaeda.”

The requests, according to the correspondence, took Pentagon staffers thousands of hours to fulfill. The sub rosa bureaucratic spat became so testy that Defense Secretary Rumsfeld wrote on October 1, 2004, “Your minority inquiry seems to be getting broader and more open-ended in scope.” In the letter, the now outgoing Pentagon chief urges Mr. Levin to reconsider his wide-ranging request for documents and to give his inquiry “constructive focus.”

At the root of Mr. Levin’s probe is his contention that an alternative analysis conducted after the attacks of September 11, 2001, by the Policy Counterterrorism Evaluation Group — and subsequent analysis from the Office of Special Plans, which was created in 2002 to prepare for the Iraq war — distorted and manipulated intelligence provided to policy-makers and Congress in the run-up to the invasion of Iraq.

The Senate select committee on intelligence’s bipartisan report on pre-war intelligence, along with the president’s own commission that examined the issue, said the intelligence reports were not influenced by the Pentagon team’s analysts or the Office of Special Plans.

Despite signing off on the Senate intelligence panel’s report, Mr. Levin has pressed on. Three months after the release of the report and two weeks before the 2004 presidential elections, Mr. Levin released his “Inquiry into the Alternative Analysis of the Issue of an Iraq-al Qaeda Relationship.” The appendix for the inquiry lists six categories of information requests the Pentagon denied the senator, including documents relating to detainee briefings for Mr. Feith’s analysts; contacts between those analysts and a pre-war opposition group, the Iraqi National Congress, and communication between the analysts and other intelligence agencies about assessments on Iraq’s ties to Al Qaeda.

A spokeswoman for Mr. Levin said this week the senator had not yet made a decision on whether to subpoena the documents.

In the report, Mr. Levin concluded that Mr. Feith failed to make key changes requested by the CIA in a report he submitted on October 27, 2003, to the Senate intelligence committee regarding that relationship. That memo was the basis of a Weekly Standard cover story by Steven Hayes touting the operational links between Saddam Hussein’s Iraq and Al Qaeda.

At the request of Mr. Feith, the CIA’s director of congressional affairs at the time, Stanley Moskowitz, checked the 2003 memo against the recommendations from his agency and concluded “after a careful comparison between that submission and what we had requested as our condition for clearance of CIA material, I believe that you made all of the changes we requested,” according to a November 1, 2004, letter obtained by the Sun.

Nonetheless, Mr. Levin in a September 22, 2005, letter to the Pentagon’s acting inspector general, Tom Gimble requested that the Defense Department watchdog investigate whether Mr. Feith sent CIA material to the Senate intelligence committee without the agency’s approval. In that letter, Mr. Levin requested that the inspector general look into 10 specific questions about alternative analysis into Iraq and Al Qaeda. It followed a more modest request from Senator Roberts, the Republican chairman of the Senate intelligence panel, to Mr. Gimble to investigate outstanding questions regarding the Office of Special Plans.

Mr. Levin earlier this month told reporters and Web loggers that he expected the inspector general report would be finished in the coming weeks and that Congress would proceed depending on what that report said.