Nearly 2m people have fled fighting in northwest Pakistan since early May, when the Pakistani army launched operations against Taliban insurgents.
The UN has launched an appeal for $543m in aid to avert a long-term humanitarian crisis.
Only 35% of that figure has been reached, but the target has taken on a new urgency now that many thousands more displaced can be expected from South Waziristan.
Pakistan has presented a unique problem for UN humanitarian officials because 80% of the displaced were not in camps set up by the UN and other agencies but were staying with family and friends in host communities.
It is very different to the displaced in Africa, where most are in camps.
Pakistan is being kept afloat by a $7.6bn International Monetary Fund loan, underscoring the need for outside help for the displaced.
UN aid operations in Pakistan cost about $2m a day.
