The Venezuelan is expected to join the 'Magpies' on a season-long loan, with Dwight Gayle heading in the other direction for the campaign.
United will pay a £2m loan fee for the 28-year-old, who is thought to have undergone his medical on Sunday.
For his part, Gayle is thought to have traveled to the Midlands to complete his side of the deal.
Newcastle boss Rafa Benitez has repeatedly spoken of his desire to add depth to his squad this summer, with Rondon now set to join Yoshinori Muto, Fabian Schar, Martin Dubravka and Ki Sung-Yeung in joining the club.
Gayle returns to one of his favourite hunting ground in the form of the Championship, where he scored 23 goals in 34 games to secure Newcastle promotion in 2016/17.