The newspaper, quoting unidentified sources, reported this week that Microsoft had told content providers of the delay. Microsoft is planning to put the Zune up against Apple Computer Inc.'s iPod, which currently accounts for more than two out of every three portable media players sold.
On Friday, Microsoft called the Post report "speculative."
"Microsoft does not have any details on Zune to share at this time," a spokeswoman said.
Microsoft last month said that it would make the Zune and a complementary online music service available this year. The latter would compete with Apple's iTunes service, which is closely tied to the iPod.
Experts, however, say the challenge won't be easy. Apple has managed to stay on top by beating competitors with better design, ease of use and marketing. Without seeing its offerings, it's impossible to say for sure whether Microsoft has a chance of becoming a serious rival.