Gayle is the issue in the deal, as Newcastle would like to see him go the other way before they can complete the signing of Rondon.
The striker failed to make an impact in the Premier League last season, but has a proven record in the Championship as he helped the 'Magpies' finish top of the division in 2016-17 with 20 goals in the campaign.
While West Brom would be interested in taking Gayle on to act as their main goalscorer, they are unwilling to pay the player's wage demands and also do not want to have a clause in the contract that would force the 'Baggies' to buy the player.
The transfer window's end is getting ever closer, and it is unclear whether Rafa Benitez has any other targets in mind, should he not be able to secure Rondon.
The Venezuelan striker scored 8 times in the Premier League last season, and is believed to be keen on the move in order to return to the top flight of Englosh football.