Both Premier League giants are keen to bringing the Croatia international to England - and know Rakitic has been frustrated in seeking a new contract at Barca.
Rakitic confirmed earlier this month he'd rejected a bumper move to PSG over the summer and had been expecting his loyalty to be rewarded with a pay-hike.
However, Barca president Josep Maria Bartomeu has since stated there's no money available to meet the player's demand.
"This season we will not be able to make the gesture that Rakitic is asking of us," he said.
"Next season we can look at it in relation to new revenue."
Watching on are both United and Chelsea, which also made enquiries after Rakitic over the summer. His current Barca deal runs to 2021.