SACRAMENTO Calif. (Reuters) - Sacramento's dark-horse bid to secure a Major League Soccer franchise won praise from league officials on Friday, who promised to continue serious negotiations with boosters led by mayor and former basketball star Kevin Johnson.

League officials touring the California capital city praised the site of a proposed downtown stadium and the success of the minor league Sacramento Republic FC, which is in the semi-finals at its level and has been selling out tickets since coming to town last spring.

"In a short period of time, what this team has come to mean to this community is remarkable," Mark Abbott, deputy commissioner of Major League Soccer, said at a news conference at a former railyard that is the site of the proposed new soccer stadium. "I leave incredibly impressed with what we've seen."

He called the city's effort "tremendous."

Abbott and other officials toured the proposed stadium site on Thursday afternoon and attended a rally and concert for fans that night. League officials met with the ownership group of the Republic, the owner of the proposed stadium site, Johnson and others.

The city is making its play for Major League Soccer just a year after Johnson led a successful effort to keep the former owners of the Sacramento Kings of the National Basketball Association from selling that franchise to a group that wanted to move it to Seattle.

If the city wins the MLS franchise, the team will play at a new $100 million stadium planned for the railyard site, near the location of a massive new sports and entertainment complex in the works for the Kings.

The plan's backers say soccer will appeal to millennials the city is already wooing with a thriving midtown hipster scene, and to Latinos, who comprise nearly a quarter of the city's residents, as well as other groups.

Sacramento was hard-hit by the economic downturn and parts of downtown remain shabby. Homeless people mingle with well-heeled lobbyists and government workers on its streets, and a 1980s-era shopping mall being demolished to make way for the Kings' arena was so neglected that the second floor sloped downward.

A soccer franchise with a downtown stadium could help revitalize the city and mark it as a regional center for sports, analysts say.

Sacramento is competing against several cities, including Minneapolis, San Antonio and Austin, Texas, for an expansion team planned by the league.

(Reporting by Sharon Bernstein; Editing by Bill Trott)