The Dutchman looks set to exit St James' Park following their relegation from the Premier League.
The full-back is attracting plenty of attention from Italy with Napoli and Inter Milan both interested in signing the 26-year-old, The Sun reports, but it is the Old Lady that are leading the chase for his signature having contacted the Magpies about a deal.
However, while Newcastle have set their asking price, The Sun claims that Juve are only willing to pay £5m for the Dutchman as they view him as something of a potential back-up option rather than a first-team regular, and are unwilling to increase the amount even though the Magpies are prepared to accept £7m if necessary.
Although injuries meant that Janmaat played a limited role during the final weeks of this past season, he will surely be one of the players that Rafael Benitez will look to - should the Spaniard himself, stay - to help the side return to the Premier League at the first attempt following their relegation.
Janmaat scored twice and contributed four assists in the top flight this term, and while his defending was sometimes questionable, the fact that United can expect to be on the front foot much more often next season should allow the Netherlands international to display his ability going forward much more regularly.