The International Monetary Fund slashed its global economic growth forecast for 2014 after the world's two biggest economies showed weakness in the early part of the year.
The US and China have suffered from weak growth and slowing domestic demand respectively.
While some of the factors behind the reduction were temporary, some richer nations face prolonged economic stagnation if they do not act to boost growth through deeper reforms, the IMF warned.
Updating its World Economic Outlook, the IMF said the global economy should grow at 3.4% this year, down 0.3% on its April prediction. Yet, the Fund's prediction for global growth in 2015 remains at 4%.
"Robust demand momentum has not yet emerged despite continued very low interest rates and easing of brakes to the recovery, including from fiscal consolidation or tight financial conditions," the IMF said.
Developed economies should keep interest rates low, the Washington-based Fund said.
Central banks across developed countries slashed interest rates in the wake of the 2008-09 financial crisis and have maintained low rates in a bid to stimulate the economic recovery.
While the IMF pointed to Japan, Germany and the UK as the year's best performers, weakness in the US and China convinced it to lower its global outlook.