Germany international midfielder Holtby has already signed a pre-contract agreement to join Spurs when he becomes a free agent at the end of the season.
But the North Londoners are thought to be pushing to bring him to White Hart Lane this month as manager Andre Villas-Boas looks to strengthen his midfield options following injury to Sandro.
The Bundesliga club last week claimed to have rejected Tottenham's offer to sign the 22-year-old this month, branding the bid "unacceptable".
Heldt says Spurs are yet to table an improved offer and reports in France suggest Schalke are waiting on that bid to help fund a move for Lyon's Michel Bastos.
The Schalke chief is hoping the situation will be resolved soon, telling L'Equipe: "We didn't have any news from Tottenham since the first proposition we refused five days ago.
"But the situation should sort itself out early this week."