GENEVA (REUTERS) - US Ambassador Dennis Shea told the World Trade Organisation on Friday that appeals rulings can be vetoed if they take longer than the allowed 90 days, throwing down a new challenge to the WTO system of enforcing global trade rules.

The WTO rules traditionally rely on "negative consensus", whereby a ruling can only be blocked if every member opposes it.

"The consequence of the Appellate Body choosing to breach (WTO dispute) rules and issue a report after the 90-day deadline would be that this report no longer qualifies as an Appellate Body report for purposes of the exceptional negative consensus adoption procedure," Shea said, according to a copy of his remarks provided to Reuters.