Washington ? A new book on the Bush political dynasty claims former President George H.W. Bush opposed last year’s invasion of Iraq.

In “The Bushes: Portrait of a Dynasty,” Peter and Rochelle Schweizer cite as evidence a summer 2002 interview in which the elder Bush’s sister said her brother had expressed his “anguish” about the administration’s preparations for war.

“But do they have an exit strategy?” the former president is quoted as worrying.

“Although he never went public with them,” the authors assert, “the president’s own father shared many of (the) concerns” of Brent Scowcroft, his national security adviser and a leading war opponent.

Top Bush aide Jean Becker denied the allegations.

“From the very first day, President Bush 41 unequivocally supported the president on the war in Iraq,” she said. “He had absolutely no reservations of any kind.”

Peter Schweizer is a research fellow at Stanford University’s conservative Hoover Institution and authored “Reagan’s War.”

The book pries open the door slightly on one of the Bush clan’s most closely held secrets: the former president’s private qualms about portions of his son’s Iraq policy.

“He agrees with the policy goals but not with all of the execution,” a close friend told the New York Daily News.

The older Bush has maintained strict public silence about possible differences, and only last week hammered “elites and intellectuals on the campaign trail” for criticizing the war.

Yet close friends and associates said the elder Bush, while fiercely proud and protective of his son, nevertheless harbors concerns about the war and its aftermath.

These sources told the Daily News that aside from his “exit-strategy” fears of a prolonged, bloody conflict, the former president was troubled that the war fractured the international coalition he painstakingly assembled to expel deposed Iraqi dictator Saddam Hussein from Kuwait in 1991.

One close associate said the elder Bush feels Vice President Dick Cheney and Secretary of Defense Donald Rumsfeld may have pushed President Bush too hard for a pre-emptive strike.

In his 1998 diplomatic memoir, the former president offered this impassioned defense of his controversial decision not to attack Baghdad and topple Saddam in 1991:

“Trying to eliminate Saddam … would have incurred incalculable human and political costs. … Had we gone the invasion route, the United States could conceivably still be an occupying power in a bitterly hostile land.”

One well-placed Bush colleague said the elder Bush recently acknowledged, “I’m having trouble with my boy,” referring to Iraq.