The 24-year-old had already announced in May that he intended to leave the Stade Auguste Bonal in the summer to further his career at a bigger club.
Lacombe has not revealed any details about the deal, which is expected to be finalised on June 13, when the French transfer window reopens.
"It is an open secret," Lacombe told RMC." [Lille president] Michel Seydoux is currently abroad.
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"We hoped to be called this afternoon, but we expect it to be tomorrow. For Marvin, it will be Lille.
"Our goal was to keep our young players in the squad until they played 100 games for us. We are happy to see them go and play at clubs who are at another level."
Martin, who broke into Sochaux's first team in 2008, has been a key player for the Montbeliard club, which has earned him regular call-ups to the France national team in recent months.
Lacombe then commented on the situation of Algeria international Ryad Boudebouz, who recently revealed that he is on Liverpool's wish list.
"If a suitable offer for Ryad arrives, we will honour our word and he will go," he told reporters.