* Judge calls Stanford a serious flight risk

* Stanford's lawyer says will appeal

* Judge's bail denial called unusual -- lawyers (Adds background, quotes from lawyer)

By Eileen O'Grady and Bruce Nichols

HOUSTON, June 30 (Reuters) - A federal judge on Tuesday ordered Texas financier Allen Stanford, accused of a $7 billion fraud, held without bail until trial.

U.S. prosecutors had argued that Stanford, who faces life in prison if convicted on all charges contained in a 21-count indictment, had the means and motive to flee.

"The court determines that Stanford is a serious flight risk and there is no condition or combination of conditions or pretrial release that would reasonably assure his appearance," U.S. District Judge David Hittner said in an order that revokes a $500,000 bond that a magistrate had granted Stanford on Thursday.

Stanford, who spent the last 15 years living in the Caribbean where he was knighted by the Antiguan government, had a network of wealthy associates and had at least two passports, prosecutors told Hittner at hearing on Monday.

"We are very disappointed and we are going to appeal to the 5th Circuit," Dick DeGuerin, Stanford's lawyer said in a statement.