"The major record labels, trade groups, and distributors appear to be making a concerted, systematic effort to stifle MP3.com's growth and undermine our ability to promote our services," said Michael Robertson, chief executive of MP3.com.

The San Diego-based company uses a music compression format that makes it easy to download and play near-CD-quality music on a home computer or a portable player.

Robertson said the latest assault came in the way of blacklisting from the Grammys quarterly magazine.

The Grammys Awards will be held next week in Los Angeles.

"If you subscribe to Grammy Magazine, the publication developed by Grammy organizers the National Academy of Recording Arts & Sciences (NARAS) ... the ad for MP3.com's artists will not appear," said Robertson.

San Diego-based MP3.com registers 200,000 visitors daily to its Web site that hosts more than 10,000 songs from more than 5,000 artists on the MP3 audio format.

While MP3 has surged in popularity with fans, it has irked the record industry because it can be used to copy and post songs on the Internet, allowing illegal duplicates of copyright music to be distributed over the Web.

MP3.com's advertising will appear, however, in the program for the Grammy Awards.

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"Apparently, our ad slipped into the awards version of the program before the Brass upstream caught wind. By the time it was noticed, it was too late to halt the printing of the actual catalog, but not too late to pull it from subsequent printings," Robertson said.

NARAS spokesman Larry Solters said, however, that "NARAS is happy and thrilled that MP3.com is advertising in the program." He declined to elaborate further, but a source close to the organization said the reason MP3.com's advertisements did not make the quarterly magazine was due to limited space and time.

"They were very late in coming and the magazine couldn't accommodate them. We have no problems with them (MP3.com. They're in the program book," the source said.

Robertson said MP3.com paid to appear in each of recording industry group's upcoming quarterly publications, but was told they were not to be used because they were too controversial.

On its Web site on Friday, MP3.com posted a letter dated Feb. 12 from NARAS advertising sales representative Brad Burkhart stating, "because of the limited number of advertising positions available in the magazine in conjunction with the somewhat controversial nature of your product, the Recording Academy has asked me to steer you away from this vehicle."

Burkhart, an independent contractor, told Reuters on Friday that he had misspoken in the letter.

"It was really inappropriate. NARAS really didn't tell me that. It was me casting my own opinion and does not reflect NARAS at all. As a result, we've been getting beat up by MP3.com," he said.