Pilot Pen Corporation of America will pull its sponsorship New Haven’s Pilot Pen Tennis Tournament after 15 years — a move that puts the city’s most attended professional sporting event in jeopardy and could cause the city to lose millions of dollars.

Though Pilot Pen has committed to one final tournament, which will take place August 20-28, 2010, the office supply company will not renew its contract, tournament director Anne Worcester said. Dennis Burleigh, Pilot Pen’s president and CEO, said in a statement Tuesday that the effect of recession on the pen industry forced the company to drop its long-standing sponsorship of the tournament. With Pilot Pen covering nearly a third of the nine-day event’s $4.5 million cost, operating “without a title sponsor is not a viable option,” Worcester said.

Each year, the tournament brings $26 million to the greater New Haven economy and attracts 20 hours of international television coverage, Worcester said. Greater New Haven Chamber of Commerce president Anthony Rescigno said the tournament’s potential termination would have damaging effects on the city and state economies.

“The city of New Haven has a lot of branding opportunities on the line through the tournament,” Rescigno said.

But Rescigno said he expects another company will want to sponsor the tournament after 2010.

Worcester said she and her colleagues at New Haven-based Connecticut Professional Tennis LLC began compiling a list of prospective sponsors Wednesday but have not released any names.

The annual event has developed into a “very desirable” investment for potential sponsors, Worcester said, because it is a family-friendly week of entertainment , both a men’s and women’s competition, and the final stop on the summer-long road to the U.S. Open. The tournament, commonly known as “The Pilot Pen,” will require significant re-branding if a new company commits to the title sponsorship, Worcester said.

Yale and City Hall have been the tournament’s hosting sponsors for as long as it has existed under the Pilot Pen name, Worcester said. In return for Yale’s investment in the tournament, the University receives exposure, on-site booths and benefits such as tickets and hospitality, she added.

Yale Director of Athletics Tom Beckett called the Pilot Pen “a tremendous event for Yale” and said the University hopes to do anything possible to help find a new title sponsor.

“We want to keep [the tournament] as the focus of tennis interest in New England and around the region,” Beckett said.

Mayor John DeStefano Jr. said in a statement that he appreciates Pilot Pen’s relationship with the city and that he hopes the tournament will survive.

“We look forward to continuing the immense success that this tournament has become,” DeStefano said in the statement.

Yale Varsity men’s tennis captain Connor Dawson ’10, who has attended the event in the past, praised the major United States Tennis Association tournament as a source of pride for both Yale and the city.

The event is held at The Connecticut Tennis Center at Yale. Caroline Wozniacki, of Denmark, and Fernando Verdasco, of Spain, won this year’s tournament, which was televised nationally by CBS Sports and ESPN2, and was attended by almost 100,000 spectators, Rescigno said.