newspaper will soon abandon its European-style "Berliner" print format and go tabloid to help stem heavy losses.
It is understood that an agreement to outsource printing to Trinity Mirror could be announced as soon as this week, although senior sources said it was not yet completely finalised. The plans mean The Guardian will be redesigned to fit smaller tabloid pages.
A source close to the negotiations said: "This deal makes great sense to the Guardian financially, according to Daily Telegraph.
"It keeps the journalism available in print, which many readers really value, and it will offer much more flexibility for the future."
The contract will also allow the newspaper to scrap or sell its three Berliner presses, which cost £50m ($88.4 million) in 2005. It spent a further £30m ($53 million) on printworks in London and Manchester.
The Guardian was the first and only major UK title to adopt the Berliner format, which is taller than tabloid and narrower than a broadsheet.
At the time The Guardian said the investment would give readers "the best of both worlds", offering "broadsheet values" and the convenience of a smaller newspaper. It said it had decided to "avoid the 'easy' short-term tabloid route".
The presses have spent an increasing proportion of time idle as readers have migrated online, however. The Guardian's average circulation in April was 154,000, compared with 341,000 in the same month in 2005.
Abandoning print entirely is not viewed as a realistic option yet by major newspapers.
At the Guardian print advertising and newsstand sales accounted for 60pc of total revenues of £209.5m ($370 million) in the year to April 2016. The proportion was down less than one percentage point on the prior year, as digital growth stalled amid the growing dominance of Google and Facebook.
A source at the newspaper said: "Despite declining circulations, there is still lots of demand for quality news in print. The current format, however, is only ever going to become more expensive to produce."
Shutting down the Berliner presses should save millions of pounds per year but could trigger a hefty one-off charge. According to the newspaper's annual report last year, it still owed Lloyds Bank £33.7m ($59.5 million) on hire-purchase agreements for the presses.
The Guardian aims to break even within two years, after operating losses of £37.8m ($66.8 million) for the year to April 2017.
Its printing contract is a boost to Trinity Mirror, as its presses will get more use. It is understood to have won the work ahead of News UK, which bid despite longstanding editorial clashes with the left-leaning title, and Johnston Press, which prints it in Northern Ireland.
The Guardian and Trinity Mirror declined to comment.
Trinity Mirror has five printworks across the country, at Watford, Birmingham, Oldham, Teesside and Glasgow.