It is feared millions of Afghans could starve
"We will be sending the cargo today. We have moved it forward because the United Nations was able to reach agreement with the Afghan side," Uzbek Emergency Situations Minister Rovshan Khaidarov told the French news agency AFP.
This will mark the first time Uzbekistan has opened its border with Afghanistan for four years, providing a major boost to the relief effort.
The UN's World Food Programme (WFP) has been stockpiling supplies, including baby food, clothing and medicines in the town of Termez.
Despite the Uzbek comments, WFP spokesman Michael Huggins told the Reuters news agency the shipments would probably not start moving until Tuesday.
He was quoted as saying barges would carry supplies across the Amudarya river into northern Afghanistan.
Tuesday's trip would be trial run and that a full shipment would cross the river on Wednesday, he said.
Satisfactory security
Uzbekistan closed its border to Afghanistan in 1997 after the Taleban captured the northern Afghan city of Mazar-e-Sharif, which is some 60 kilometres (38 miles) from Termez.
But now that the city has been retaken by the opposition Northern Alliance, it appears the UN is satisfied about the security of an aid operation from Termez into Afghanistan.
A convoy of trucks from the UN's children's charity, UNICEF, set off on Monday from the Uzbek capital, Tashkent, heading for Termez.
It is carrying 10,000 blankets, thousands of winter coats, warm boots and soap and detergent.
From Termez, aid then has to cross the Amurdarya river.
The UN believes there are some 70,000 displaced Afghans around Mazar-e-Sharif.
Aid workers say millions of Afghans face starvation as winter sets in if aid operations are not successful.
Even before the US military campaign began, Afghans were facing food shortages, largely because of a prolonged drought.
UN Secretary General Kofi Annan warned earlier this month that the UN was only distributing half the aid it had hoped to get to Afghanistan.