A German newspaper report started the gossip, claiming that Toyota was keen to replace Schumacher because his countryman Heidfeld's wage bill is as much as half the size.
Heidfeld's BMW-Sauber contract expires at the end of the year, amid separate speculation that Schumacher or Sebastian Vettel are better placed to race alongside Robert Kubica in 2008.
Should Ralf lose his seat, it has been suggested that he is unlikely to find another spot on the grid.
But Heidfeld, 29, said at Sepang: "I don't think Ralf has to worry. He is one of the best drivers in formula one.
"I am very happy with BMW and I hope that it continues like that," he told the television network Premiere.
Ralf, insisting that it is "still much too early" to talk about next year, responded: "I can only return the compliment to Nick.
"He is having a very good season and it looks like he has no reason at all to leave (BMW).
"For the time being I am concentrating on my season, and there is a lot to do," said Schumacher, who was ninth quickest in the morning session in Malaysia.
04/05/07 According to the Bild newspaper, Toyota have already approached Heidfeld's management in a bid to sign the German for next year's Championship. The team is allegedly keen to replace Ralf Schumacher, whose contract expires at the end of this year. However, Toyota have denied these reports, saying they are not yet considering their 2008 driver line-up.
"This is only the second race of the season and we are not yet at the stage of looking at driver options for the future," team manager Richard Cregan told Autosport. "We are very happy with the driver line-up we have now and we have made no such contact. Instead we are concentrating on our race program for 2007."
Both Ralf and Heidfeld will be out of contract at the end of this season, however, Toyota do have a two-year option on Ralf.
04/05/07 Toyota has launched a bid to replace Ralf Schumacher at the end of the season with BMW's Nick Heidfeld, according to the German newspaper Bild.
Both drivers' contracts expire this year.
29-year-old Heidfeld's manager Werner Heinz said: "We have the offers of two top teams on the table."
'Bild' claims that the second offer has come from Honda, sparking speculation that the German driver is almost certain to leave BMW Sauber.
Countryman Ralf Schumacher, meanwhile, retains close links with BMW motor sport director Mario Theissen following his five-year stint at Williams that ended in 2004.
'Bild' said Toyota can only hold Schumacher, 31, to a two-year option on his current contract if the Japanese squad is in the top three of the constructors' championship.