United are keen on winger James Rodriguez and fullback Alex Sandro, Spurs are chasing Joao Moutinho and Chelsea want Jackson Martinez.
"When the time comes to contact with me, they will learn we're not interested. I will not let anyone leave. If FC Porto is a title shot and is in the knockout round of the Champions League why would we sell a player?" said president Pinto da Costa.
"Of the regulars, those who the coach deems necessary, someone will only leave if they pay the release clause."