Sun Microsystems is expected to announce tomorrow that it_s spending more money in its effort to lure Internet companies and start-ups.

Less than a month ago, Sun unveiled a $300 million effort for co-marketing, discounted products and incentives to attract companies in their early stages. The Palo Alto, Calif., company will bolster that with another $200 million tomorrow and will expand the effort to Europe, Asia and the Middle East, sources said. Companies such as Sun, IBM, Compaq Computer, Hewlett-Packard and Dell Computer are fighting to attract new Internet companies as fast as possible. These companies could become large and important customers as the Internet spreads into more corners of everyday life. Close ties with start-ups, involving equity investments, also are a way for big companies to profit from the entrepreneurial boom in the way venture capitalists have. Sun is widely viewed as the first company that start-ups turn to for servers to power their Internet sites, but evidently it is feeling the heat from the hundreds of millions of dollars rivals are sinking into their programs. The company also started a partnership with Broadvision, whose software customizes Web sites for visitors based on browsing behavior. The plan for joint software development and marketing is interesting because Broadvision was one of HP_s early partners. Broadvision will incorporate Java 2 Enterprise Edition, a collection of software components from Sun that makes it easier to run e-commerce software on back-end servers. Though the collection initially met with a chilly reception, flexibility by Sun has led to new licensees.