Pakistan has so far refused to open the border, forcing refugees to wait in a 200-metre strip of no-man's-land between the two countries.
Click here for map of the refugee situation
Fatoumata Kaba, a spokeswoman for the UN refugee agency, the UNHCR, said 100 tents and food had been delivered to the area and would be distributed to refugees.
But she did not think Pakistan would give in to appeals to immediately open the borders to let the refugees through.
"I don't think this is going to happen today or tomorrow, it might take a major event inside Afghanistan before that happens, but I'm not sure what that might be," Ms Kaba said.
In scuffles at the Chaman crossing on Sunday, Pakistani border guards fired shots at hundreds of Afghans demanding to enter the country.
Reports said five people were injured, including a 13-year-old boy.
The guards then opened the border for a short while to ease the pressure on the Afghanistan side.
UN sends more food
The UN World Food Programme (WFP) has been granted permission to cross the border into the no-man's-land in Chaman to deliver food and supplies.
WFP spokesman Francisco Luna said that a delivery would be made on Monday of some 20 tonnes of biscuits, flour, food oil and other supplies.
The food should last about 5,000 refugees for five days.
Mr Luna said the WFP had enough food stored in Pakistan's border cities of Peshawar and Quetta to cover the foreseeable basic needs of 300,000 people.
Looming crisis
The US is taking military action against the ruling Taleban in Afghanistan for harbouring Osama Bin Laden, chief suspect for the 11 September terror attacks on New York and Washington.
But the UN has warned that as many as 1.5 million people may be displaced if the military action continues, with as many as 300,000 Afghans seeking refuge in Pakistan this year alone.
"We are concerned that thousands of people are approaching the border," said UNHCR spokesman Peter Kessler.
"We haven't seen a refugee flood yet but all the ingredients are there," he said.
Even before the American strikes, Pakistan was sheltering about two million Afghans who had fled after years of civil war and drought.
Grim future
Pakistani officials say 50,000 Afghans have crossed into Pakistan since the crisis began. But even inside Pakistan, the refugees face a grim future.
The Pakistani Government only allows new refugee camps to be built in the border area, a remote and inhospitable region.
The area also lacks much basic infrastructure making it harder to supply essentials such as water, a situation exacerbated by the region-wide drought.
Aid agencies said their work is often hampered by attacks on their staff in an area that is notoriously insecure.
However, the Taleban have ended their occupation of a UN office in northern Afghanistan after their supreme leader issued a decree ordering the return of looted assets of international aid agencies.
A UN official in the Pakistani capital Islamabad confirmed that the Taleban had withdrawn from the office in the city of Mazar-e-Sharif and described it as a "step in the right direction".
The Taleban leader, Mullah Mohammad Omar, has also ordered that UN facilities in Afghanistan should be given protection.
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