The share of global trade done on WTO terms has fallen to 72% and could fall further, amid the biggest disruption to the international trading system in the past 80 years, the director-general of the World Trade Organization told Reuters Tuesday.

"We're experiencing the largest disruption to global trade rules, unprecedented in the past 80 years," Ngozi Okonjo-Iweala said in an interview at the start of her second term at the helm of the Geneva-based trade watchdog.

"So it's not surprising that some would question the global trading system... and predictability,” she added, while pointing to signs of resilience.

Since the introduction of U.S. President Donald Trump administration's tariffs, the share of global trade conducted under the WTO's Most-Favored-Nation (MFN) terms is down from about 80%, WTO data shows. The principle requires WTO members to treat all others the same.