WASHINGTON — WASHINGTON—The special prosecutor investigating Vice President Dick Cheney's former chief of staff, I. Lewis "Scooter" Libby, has amended one of the allegations against the White House aide that was contained in documents filed in federal court last week.

The change downplays the importance that the CIA gave to Iraq's purported attempt to buy uranium from the African nation of Niger. Further, Special Counsel Patrick Fitzgerald corrected the allegation that Libby had described the suspected uranium purchase as a "key judgment" of the CIA—a term of art in the intelligence community that gives the accusation high significance.

In papers filed Tuesday, Fitzgerald amended a single sentence on page 23 of the 39-page document he filed last week. The sentence dealt with what information Libby supposedly was to tell former New York Times reporter Judith Miller from the CIA's 2002 National Intelligence Estimate—a document that covered a range of intelligence about Iraq and its efforts to acquire weapons of mass destruction.

The original sentence read: "Defendant understood that he was to tell Miller, among other things, that a key judgment of the NIE held that Iraq was `vigorously trying to procure' uranium."

Fitzgerald's corrected version said: "Defendant understood that he was to tell Miller, among other things, some of the key judgments of the NIE, and that the NIE stated that Iraq was `vigorously trying to procure' uranium."

Knight Ridder Newspapers reported earlier that the purported uranium acquisition was never part of the NIE's "key judgments" and that some CIA officials and the State Department's intelligence bureau did not believe Iraq ever sought supplies of uranium from Niger.

It also was reported by Knight Ridder that the documents that supported the attempted uranium purchase were forgeries.