A Rhode Island man has sued Cristiano Ronaldo over the phrase 'CR7', which is used by soccer fans around the world as shorthand for the Real Madrid forward.

Christopher Renzi filed the lawsuit on Monday in the US District Court in Providence against the Portuguese soccer star and a Danish company, JBS Textile Group. The firm sells underwear with the phrase 'CR7', a combination of Ronaldo's initials and jersey number.

Renzi's lawyer said on Thursday that his client was prompted to file the lawsuit against one of the world's most famous athletes after JBS Textile lawyers threatened his client with aggressive action and petitioned to cancel his trademark.

"The other side says he is trying to trade on Ronaldo's fame, and there's really nothing to that," lawyer Michael Feldhuhn said. "I knew who Ronaldo was and I didn't think of CR7 as some kind of famous trademark."

Renzi applied to the US Patent and Trademark Office for the trademark in 2008 and it was granted in 2009. His lawyer says Renzi uses 'CR7' - a combination of Renzi's own initials and the day he was born, Oct 7. - on clothing and for a seven-minute exercise program.

Feldhuhn said the European textile company had offered Renzi money to stop using the trademark. He wouldn't say how much but said it was "very small".

JBS Textile's lawyer, Eric Fingerhut, would not comment.

The lawsuit asks the court to declare Renzi is not infringing any trademark owned by Ronaldo or JBS.

JBS Textile sells CR7 underwear and socks for men and boys in Europe. According to a letter sent to Renzi from the company's lawyers, it has plans to start selling in the US soon.