Former US top diplomat Hillary Clinton and her staff fought "tooth and nail" to push ideas for diplomacy in Afghanistan in a bitter turf war with the White House, an ex-official says in a new book.

Vali Nasr, now dean of the Paul H. Nitze School of Advanced International Studies at Johns Hopkins University, was an advisor to Richard Holbrooke, the special representative to Afghanistan and Pakistan until his death in 2010.

US President Barack Obama inherited the legacy of the 2001 US-invasion of Afghanistan and vowed to wind down the war when he entered the White House.

But in an excerpt from his new book, "The Dispensable Nation: American Foreign Policy in Retreat," Nasr says "my time in the Obama administration turned out to be a deeply disillusioning experience."

Clinton, who stepped down after four years as secretary of state in January, whenever possible went directly to Obama in regular private weekly meetings which she had insisted on as a condition for taking the job.

That allowed her to get "around the so-called Berlin Wall of staffers who shielded Obama from any option or idea they did not want him to consider," Nasr wrote in the excerpt in the online Foreign Policy magazine Monday.

"Clinton got along well with Obama, but on Afghanistan and Pakistan the State Department had to fight tooth and nail just to have a hearing at the White House," he said.

"Had it not been for Clinton's tenacity and the respect she commanded, the State Department would have had no influence on policymaking whatsoever."

Specifically, Clinton pushed Holbrook's idea that Washington should be trying to facilitate reconciliation talks with the Taliban as a way of ending the Afghan conflict.

White House staffers had been suspicious of Holbrooke, and blocked the idea worried that Taliban talks would only expand his influence, he said.

And the military thought that talk of political reconciliation as a path out of Afghanistan would only undermine an effective counter-insurgency strategy.

"The White House encouraged the US ambassadors in Afghanistan and Pakistan to go around the State Department and work with the White House directly, undermining their own agency," he alleged.

"Those ambassadors quickly learned how easy it was to manipulate the administration's animus toward Holbrooke to their own advantage."

State Department deputy acting spokesman Patrick Ventrell Monday refused to discuss the book, but said "we make our input" adding his department had "an excellent working relationship with the White House."

"We really stand behind the record of the progress we've made in Afghanistan, but beyond that, I'm not going to get into interagency discussion."

Nasr however describes a bitter battle to coax the White House around to the idea of Taliban reconciliation talks, which took more than a year of lobbying.

"Victories for the State Department were few and hard fought," he writes.

"It was little consolation that its recommendations on reconciliation with the Taliban or regional diplomacy to end the Afghan war eventually became official policy -- after the White House exhausted the alternatives."