New Delhi, Sept. 15 -- Trade wars may promise an advantage for individual countries, but when governments respond to tariffs with more tariffs, the economic damage can spread across the entire world. A new World Trade Organization (WTO) report warns that a further breakdown in global trade cooperation could sharply reduce economic output and exports, with the poorest countries facing some of the steepest losses.

The WTO's economists modelled what could happen if the global economy split into competing geopolitical blocs. By 2050, global GDP would be 5.1% lower and exports 18.6% lower than under a more cooperative system, according to the report.

In a more severe scenario, where the WTO is replaced by a patchwork of free trade agreements...