Fenerbahce chief Damien Comolli is returning to Tottenham for a new signing.
And former Spurs director of football Comolli, newly appointed to a similar role with the Turkish club, is leading their bid to sign the midfielder.
Spurs paid Newcastle £30million for Sissoko, 29, two summers ago.
However the France international started just 15 Premier League games last season, although he came on as a sub a further 18 times and scored once.
Capped 53 times, he was named in Les Bleus' standby list for this summer's World Cup finals.
Paris-born Sissoko is under contract with Tottenham until 2021.