At a time when Yasser Arafat was regarded as a diplomatic pariah by the U.S. government, former President Jimmy Carter secretly coached the Palestinian leader to improve his image, drafted passages for Arafat's public speeches and counseled other leaders of the Palestinian uprising in Israeli-occupied territories, according to a forthcoming book.

"There was no world leader Jimmy Carter was more eager to know than Yasser Arafat," the historian Douglas Brinkley wrote in "The Unfinished Presidency: Jimmy Carter's Journey Beyond the White House" to be published in May by Viking. "Carter felt certain affinities with the Palestinian: a tendency toward hyperactivity and a workaholic disposition. Both men were like modern Bedouins with airplanes instead of camels," always moving.The book portrays the former Georgia governor as a messianic character, infused with righteousness, working Arab back channels to change Middle East equations.

From their first meeting in 1990, Carter and Arafat "stayed in constant communication," Brinkley writes. While Arafat agreed to "distance himself" from radical elements in the Palestine Liberation Organization, Carter encouraged the PLO chairman to describe the Palestinian plight to the "world community" in speeches designed "to secure maximum sympathy."

It could not be determined if Arafat ever used Carter's precise language, but the PLO leader did adopt a less belligerent way of talking about Palestinian distress. At the time of the Carter letter, Arafat was still struggling to overcome the pariah status he acquired during his organization's years of violent resistance. The PLO would eventually win full recognition from the United States when Arafat appeared with the late Israeli Prime Minister Yitzhak Rabin at a White House peace ceremony in 1993.

Brinkley, who interrupted plans for a three-volume biography of the 39th president to concentrate on Carter's career after leaving the White House, said he was given "full access to Carter's postpresidential papers and trip reports."

The historian conducted numerous interviews with Carter and accompanied him on trips to the Middle East and Haiti to gather material. Although the 73-year-old former president has reviewed the manuscript, Brinkley said it was agreed that the book "would be unauthorized so I would be free to draw my own conclusions."

Brinkley, a professor of history and director of the Eisenhower Center at the University of New Orleans, made page proofs of the 500-page book available to The Boston Globe.