WRAPUP 6-Clinton attacks Obama as all talk, little substance

(Updates with Brownsville event, adds McCain story in New York Times, changes dateline from HIDALGO)

By Steve Holland

BROWNSVILLE, Texas, Feb 20 (Reuters) - Democratic candidate Hillary Clinton criticized rival Barack Obama as a big dreamer with little substance on Wednesday as she sought to slow his momentum from 10 straight victories in the race for the party's U.S. presidential nomination.

"We need to dream big, but you know, dreams alone won't make anything," Clinton said while courting Hispanics at a noisy rally in this south Texas town on the Mexican border. "We've got to have solutions to the problems that face us."

The New York senator and former first lady sharpened her message against Obama before the March 4 Democratic nominating contests in Texas and Ohio, which have become critical to her presidential aspirations after losses to Obama in Wisconsin and Hawaii.

But support mounted for the first-term Illinois senator, whose "yes we can" message and powerful speaking style has propelled him to the front-runner's position. The 1.25 million member Teamsters union formally endorsed him on Wednesday.

His long string of victories put Clinton in the awkward position of telling supporters, in media interviews and speeches, "Don't give up on this!" and "This campaign goes on!" while her aides explained how she would close the gap with Obama by the time of the Puerto Rico contest in June.

She and Obama crisscrossed Texas on Wednesday and will face off in a crucial debate on Thursday in Austin.

In the Republican race, likely nominee John McCain's campaign angrily rejected a report in The New York Times that he had a close relationship with a female lobbyist eight years ago that the paper suggested had undermined his stance as a promoter of high ethics among lawmakers.