The methods, such as sleep deprivation, confinement in small spaces and waterboarding, will be described as having gone beyond what was "legally allowable", CBS News reported.
That, in common parlance, would be torture.
Ms Feinstein faced intense pressure last night to at least delay publication of the tract.
While US President Barack Obama has indicated support for its release, US Secretary of State John Kerry asked Ms Feinstein last week to consider the possible fallout.
But Ms Feinstein will be mindful that once control of the US Senate and therefore of the Intelligence Committee passes to the Republicans next year, the chances of the conclusions of the investigation into what the CIA did in the wake of 9/11 in the name of national security may never be made public.
Guards escort a detainee at Guantanamo Bay, where it is alleged torture took place under the Bush administration. Photo / AP
The report is also expected to accuse the CIA of lying to the then administration of President George W Bush about its activities - an assertion that top agency officials from the period and Mr Bush himself have already started to push back against.
The warnings to overseas installations about the report were delivered by the State Department.
It urged all overseas posts to "review their security posture" for a "range of reactions".
Release welcomed by human rights advocates
Among those demanding that it be released are human rights groups.
"Maintaining secrecy around a defunct torture programme is the real liability as doing so denies us the right to debate what happened and make sure it is never repeated," said Sarah Margon of Human Rights Watch.
But the Republican chairman of the House Intelligence Committee, Mike Rogers, has been outspoken in his opposition.
"I think this is a terrible idea," he said on CNN. "Foreign leaders have approached the government and said, 'You do this, this will cause violence and deaths'."
It is clear, meanwhile, that those who led the CIA and its interrogation efforts during the years in question will aggressively challenge the accuracy of the report and that Mr Bush will support them.
"We're fortunate to have men and women who work hard at the CIA serving on our behalf," he said at the weekend. "These are patriots and whatever the report says, if it diminishes their contributions to our country, it is way off base."
John McLaughlin, former deputy and acting director of the agency, commented: "Once the release occurs, we'll have things to say and will be making some documents available that bear on the case."
He added that in his view the report "uses information selectively, often distorts to make its points".
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- Independent
