The former Tottenham right-back is unsettled on Tyneside and has designs on a move back south. And United boss Glenn Roeder could attempt to include Carr as a makeweight in a deal for Fulham midfielder Steed Malbranque.
Jermain Defoe is another potential target in a cash plus Carr deal, but it is unlikely that Spurs boss Martin Jol will be interested in taking the Irishman back to White Hart Lane.
Carr, now 29, arrived at Newcastle from Tottenham for £2 million in the summer of 2004 but has struggled to recapture his best form during an injury-affected two years.