Kimi Raikkonen, who is returning to Ferrari next season, is to miss the final two races of the season because of back surgery, leaving his seat at Lotus free for the grands prix in the United States and Brazil.
Hulkenberg is said to be in the running to replace the Finn but will stick with Sauber for the end of the season, Heinz told Bild.
"We had an offer from Lotus and we have discussed it," said Heinz. "We decided that Nico will drive the last two races with Sauber."
Former McLaren and Caterham driver Heikki Kovalainen is now reportedly in line to drive the final two races for Lotus.