The 22-year-old took part in the U21 European Championship, and has one senior England cap to his name.
Sunderland are believed to be one of the two clubs, while Everton and West Ham have also been linked with the forward.
"We are respecting the request of the two clubs not to state who they are at this stage," said Preston chairman Derek Shaw.
"It is now down to Nugent and his representatives to talk to the two clubs."
Preston made an enguiry for Iron striker Billy Sharp earlier in the summer, but were priced out of the market.
With £7m in their pocket from selling Nugent they may be willing to match United's asking price of £2m plus add-ons.
Nugent moved to Preston from League Two outfit Bury for £100,000 in January 2005.
He has scored 33 goals in 94 Championship games for the Lilywhites.
Sunderland are believed to be one of the two clubs, while Everton and West Ham have also been linked with the forward.
"We are respecting the request of the two clubs not to state who they are at this stage," said Preston chairman Derek Shaw.
"It is now down to Nugent and his representatives to talk to the two clubs."
Preston made an enguiry for Iron striker Billy Sharp earlier in the summer, but were priced out of the market.
With £7m in their pocket from selling Nugent they may be willing to match United's asking price of £2m plus add-ons.
Nugent moved to Preston from League Two outfit Bury for £100,000 in January 2005.
He has scored 33 goals in 94 Championship games for the Lilywhites.