Assombalonga has been out of action with an ankle injury since the middle of December but is slowly getting up to speed and returned to first-team training this week.
The forward has been identified by Marcelo Bielsa’s staff as a potential replacement for departed Arsenal loanee Eddie Nketiah, who returned to the Emirates earlier this month.
The report states that Leeds are looking to sign a new striker before their game against Millwall next Tuesday, meaning talks would need to commence as soon as possible to get a deal over the line.
Assombalonga joined Middlesbrough from Nottingham Forest for a club-record fee of £15 million back in the summer of 2017. Since then, he has scored 37 goals in 111 games in all competitions.
During his spell on the sidelines, Ashley Fletcher and Rudy Gestede have been given the solitary striker role under Jonathan Woodgate, with both players impressing.
On the other hand, Leeds have won one game in their last seven in the Championship, and have not scored in each of their last three games in all competitions.
There is plenty of pressure on former Boro striker Patrick Bamford, and Bielsa is looking for a proven Championship goalscorer to provide competition, and Assomablonga would fit the bill perfectly.
However, given the amount Boro spent on the forward three seasons ago, presumably they would be looking to recuperate most, if not all, of the fee paid to Nottingham Forest.