NEW YORK (CNN/Money) - Activist Ralph Nader is calling on 18-year old basketball star LeBron James to push Nike Inc. to improve the work conditions of those making its products.

The athletic shoe and apparel maker is paying the young basketball star a reported $90 million over the next seven years. It also has a new signature shoe for James due to hit the stores Dec. 20.

YOUR E-MAIL ALERTS Follow the news that matters to you. Create your own alert to be notified on topics you're interested in. Or, visit Popular Alerts for suggestions. Manage alerts | What is this?

In a letter to James he made public Thursday, Nader asked the young star to attend a presentation about conditions in Nike's overseas plants set for next Tuesday in Cleveland, home of James' basketball team, the Cavaliers.

"Mr. James, you are in a unique position to stand up for the people who make the products you endorse and to make the world a better place in the process. You can improve their working conditions in the contracted factories and pressure the entire sports shoe and apparel industry to change," Nader said in his letter to James.

A spokeswoman for James acknowledged receiving the letter from Nader, but had no comment. Spokesmen with Nike were not immediately available for comment either.

Related stories • LeBron: $100M bargain • Getting your LeBron shirt • Nike endorsements hit $1.4B

This is the second appeal that Nader has made to James. The first was in April, when James was still in high school, before he was drafted first by the National Basketball Association or signed with Nike.

In that initial appeal, Nader had asked James to negotiate an anti-sweatshop provisions in any shoe deal he signed. James was in demand by all the major athletic shoe and apparel makers.