Chelsea are demanding a loan fee for the striker, who has fallen out of favour at Stamford Bridge since the return of Jose Mourinho.
Newcastle are willing to pay £1m to take the 28-year-old for the season, according to west London sources.
But Chelsea – who paid £7m for Ba in January – are looking for around three times that figure for the striker.
Ba recently indicated he is unwilling to spend a campaign on the bench at Chelsea, who activated a release clause in his Newcastle contract while Rafa Benitez was in charge at Stamford Bridge.
The Senegal international has also been offered to clubs on a permanent deal for a fee of around £10m.
United’s only signing so far this summer, striker Loic Remy, came on a £2m loan from Queens Park Rangers.