OMAHA (DTN) -- The head of the World Trade Organization raised concern over the rising number of bilateral and regional trade agreements, citing the development as a "significant challenge" to the multilateral trading system. WTO Director-General Supachai Panitchpakdi noted that 21 such agreements were notified to the WTO between January and August 2004 alone, increasing the total number of notified agreements to more than 200. The continued rise makes preferential discriminatory trade relations "an ever more established and perhaps irreversible feature of the international trading system," a report warned.