Former Ambassador Joseph C. Wilson (search) will reveal the name of the person he thinks leaked his wife's identity as an undercover CIA (search) officer in a book due out in May, his publisher said Tuesday.

A federal grand jury has heard testimony from at least four White House officials in its investigation to identify the leaker of Valerie Plame's (search) name to syndicated columnist Robert Novak, who published the name in his syndicated column last July. Numerous other officials have been interviewed by the FBI.

Spokeswoman Karen Auerbach of the Avalon Publishing Group in New York said she did not know the identity of the purported leaker.

Novak said in his July 14 column that his sources were two unidentified senior administration officials. Novak has not commented about the matter during the grand jury investigation.

Wilson's book, "The Politics of Truth," is scheduled to come out May 20.

Publication of the book and Wilson's accompanying promotional tour could have political overtones because he is now a foreign policy adviser to Democratic presidential front-runner John Kerry. Democrats are seeking to raise questions of credibility in the minds of voters about the reasons President Bush went to war.

Wilson did not return telephone calls seeking comment for this story. He has previously contended that White House political adviser Karl Rove (search) condoned the leak but was not the actual leaker.

After Novak's column appeared, Wilson said other reporters told him that Rove had characterized Plame as "fair game" because of Wilson's criticism of the White House's uses of intelligence before the Iraq war.

The White House has repeatedly denied that Rove was the leaker.

Wilson was enlisted by the CIA to investigate whether Iraq tried to buy uranium from Niger (search). He said he found no evidence of such an attempt and has accused the Bush administration of exaggerating Iraq's nuclear capabilities to build support for war.

A description of the book on the publishing company's Web site says Wilson's conclusions about the Niger uranium were "brushed aside" by the administration.

The grand jury has continued to meet regularly in Washington under the direction of U.S. Attorney Patrick Fitzgerald of Chicago, who was appointed by Deputy Attorney General James Comey to oversee the probe. Attorney General John Ashcroft disqualified himself from the case in December in the face of Democratic criticism of his close political ties to the White House.

The leaker could be charged with a felony that carries a sentence of up to 10 years in prison.