LEXINGTON, Kentucky -- Tim Smith, National Thoroughbred Racing Association commissioner and CEO since the league office was launched in April 1998, resigned Tuesday.

The NTRA Board of Directors named vice chairman and Breeders' Cup president D.G. Van Clief Jr. acting commissioner and CEO and promoted deputy commissioner Greg Avioli to president/COO of the NTRA.

"Tim is leaving the NTRA and the sport of horse racing stronger and better equipped to compete in today's sports and entertainment market than when we started," Van Clief said. "We know that he will be successful in his next venture and look forward to his continued input and expertise." Under Smith's stewardship, the NTRA emerged as Thoroughbred racing's leading national organization, increasing the sport's exposure on network and national cable television, growing national sponsorship and expanding and coordinating the industry's legislative and lobbying initiatives.

Before joining the NTRA as its first chief executive, Smith was instrumental in bringing together several leading Thoroughbred ownership and breeding organizations to form the National Thoroughbred Association, a precursor to the NTRA.

"The NTRA has come a long way since 1998, thanks to the collaboration and persistence of many different entities and individuals," Smith said. "I am grateful to all of them and confident that, with sustained support for a true national office, still more progress for the industry lies ahead."

Van Clief was named founding chairman of the NTRA and served as its interim chief executive officer until April 1998, when Smith was appointed. In 1998, Van Clief received the Eclipse Award of Merit for his years of service to Thoroughbred racing.

The Board of Directors also announced Tuesday that CITGO Petroleum Corporation has entered into a five-year sponsorship and advertising agreement with the NTRA.

The deal designates CITGO as the official league sponsor from 2005-09.

"CITGO is proud to become an official league sponsor of the NTRA," said Don Rucks, manager of advertising and special events for CITGO. "As evidenced by television ratings, corporate involvement, media attention and other factors, Thoroughbred racing is clearly on the rise and CITGO wants very much to continue to be a part of the upswing."