Jose Mourinho had earmarked the duo as his third and fourth signings of the summer following the arrival of Victor Lindelof and Romelu Lukaku from Benfica and Everton respectively, but could have to look elsewhere after failing to convince either club to sell.
The Portuguese manager is keen to add another attacking player to his lineup before the start of the season and had identified Perisic as the ideal player to add potency to the attack from the wide areas. But in a recent press conference he revealed that he had no idea if the club would complete a deal for the winger.
United had made a bid for the Croatia international, but according to the Telegraph, they were nowhere close to matching the Serie A outfit's £49m ($63.8m) valuation with reports suggesting that the 20-time English champions were hoping to complete the deal for around £40m.
The Red Devils and Perisic were hoping to push through an agreement by Tuesday (18 July) as Inter were set to travel to China for their pre-season tour. The two clubs failed to reach an agreement, which saw the Croatian winger join the tour party to Nanjing in East Asia rather than travel to Houston in the United States to join up with United.
Dier, on the other hand, was Mourinho's first choice target as he seeks to strengthen his midfield for the upcoming campaign. The former Chelsea and Real Madrid boss is desperate to sign a holding midfielder and was keen on bringing the England international to Old Trafford this summer.
United were ready to spend up to £60m to sign Dier this summer, but Spurs were unwilling to allow him to leave. Mauricio Pochettino considers him a key player and made it clear to the club's hierarchy that he is not surplus to requirements.
The former Sporting Lisbon player is contracted to the north London club until the summer of 2021 and hence will be at the mercy at the club despite him being keen on a move up north. According to the Mirror, United have now given up hope of signing him and will turn their attention elsewhere.
Mourinho could switch targets after failing in both moves, but the Perisic transfer saga is unlikely to have ended as United still have plenty of time before the transfer window shuts on 31 August to get the move over the line. Dier, however, looks unlikely to move and the Portuguese coach will have to look at other options like Nemanja Matic, who has also been linked with a move in recent weeks.