Mayor Larry O’Brien backed away yesterday from earlier statements that he does not have a conflict of interest in a military trade show scheduled for May 27 and 28 at Lansdowne Park.

Calian Technologies Ltd., founded by O’Brien, will have a booth at the CANSEC 2009 trade show, which is the first such event there since the city banned military trade shows on city property 20 years ago.

“If there is a technical conflict of interest because I own a small percentage of the company, then I will very definitely step back from the debate,” O’Brien said. “I certainly didn’t perceive one … I certainly would not contravene any laws so I obviously will get some advice on that.”

The 1989 ban — put in place after objections to the ARMX trade show, which included offensive weapons — quietly expired when Lansdowne Park was sold in 1999.