A fourth planeload of humanitarian aid provided by the United Nations Children's Fund (UNICEF) has arrived at the Uzbekistan river port of Termez on the Afghan border, but officials have not given the go-ahead to move it into Afghanistan.
U-N officials say Uzbek border guards are not allowing the aid to be loaded on barges to cross the Amu Darya river and enter Afghanistan.
The Uzbek government last month reached agreement with U-N representatives for the aid to pass through Uzbekistan.
However, a road bridge over the Amu Darya river is closed, and Uzbek authorities do not want to open it until the nearby Afghan city of Mazar-e-Sharif has been liberated from the control of Afghanistan's Taleban rulers.
Relief officials are rushing to get the humanitarian supplies to Afghanistan before cold weather shuts down the transportation routes.