CHICAGO (Reuters) - Major League Baseball still faces an uncertain U.S. economy that led to lower attendance and financial losses at some clubs this year, the commissioner of the U.S. sports league said on Thursday.

"I've said this all year and I'll say it again, we're living in the most difficult economic environment since the Great Depression," Bud Selig said to reporters at a meeting of owners in a hotel here.

"We don't live in a bubble," he said, acknowledging that some clubs he would not identify lost money this season.

The league's regular-season attendance fell 6.6 percent to 73.4 million in its recently completed season as consumers dialed back spending in the weak economy. The teams with the biggest declines were in markets that suffered from high unemployment, including Detroit, Cincinnati, San Diego, Oakland and the Florida Marlins in Miami.

Over the past year, most sports have been hurt as corporate backers also cut spending on tickets and sponsorships.

Selig did not say where league revenue would finish compared with last year's $6.5 billion, saying some areas of the business were down and others were flat. Helping baseball was the January launch of its TV channel, MLB Network.

However, a source familiar with league finances, who asked not to be identified, said revenue would likely finish about flat.

Selig said it was too early to say what demand was like for next year's tickets, but said his concerns about the economy have not eased.

"I haven't talked to an economist yet ... who would tell me why I shouldn't be as concerned," he said when asked to compare his feelings with last year at this time.

When asked about the sales process of the Texas Rangers, Selig said he is awaiting bids, which are due on Friday. He declined to discuss whether baseball would support owner Tom Hicks reconstituting his ownership group to maintain control of the team.

Three groups are interested in buying the team and analysts expect bids in the range of $500 million to $550 million.

Billionaire sports tycoon Hicks is working to satisfy creditors who in April declared his sports group, which also owns the Dallas Stars National Hockey League team, in default on $525 million in loans. Hicks separately owns half of the English Premier League's Liverpool soccer club.

(Reporting by Ben Klayman, editing by Matthew Lewis)