If United are successful in signing Haaland, Martial would arguably be surplus to requirements with Edinson Cavani potentially set to spend another season at Old Trafford.
The Red Devils signed Martial from Monaco for £56m in 2015, and he has since scored 78 goals in 254 appearances.
After netting 11 times in his first Premier League campaign, he has since returned top-flight tallies of four, nine, 10 and 17 goals in subsequent seasons.
Inter have Serie A’s second-highest scorer this season in ex-United man Lukaku, who is two behind Cristiano Ronaldo with 17 goals so far.
But the Italian club are expected to be in the market for attacking reinforcements this summer, as Lautaro Martinez is one of the most-wanted strikers in Europe and Martin Satriano has been linked with Arsenal and Chelsea.