The United Nations said Tuesday that only a fraction of flood victims in Pakistan have received any help.

U.N. officials called on nations to turn their pledges of aid into actual donations.  

So far, the U.N. says it has received about 35 percent of the $460 million it asked for last week.

The World Bank has said it will provide $900 million to fund relief.

A World Bank news release said $10 million will be shifted from other projects to provide fuel, steel, cement and other supplies needed in the early stages of recovery.

It did not specify how the bulk of the money will be spent.

The World Food Program said Tuesday it is battling washed-out roads and bridges with many areas accessible only by helicopter.  The group said it has provided a one-month supply of food to about 1 million people since the flooding began.  

Three weeks of monsoon rains have triggered Pakistan's worst flooding, with an estimated 1,600 people killed and 20 million affected in Khyber-Pakhtunkhwa, Punjab and Sindh provinces.

The World Bank also said it planned future projects to repair critical infrastructure along the Indus River to help with future flood prevention.

The World Food Program appealed for more money, saying it will need significant donations to be able to continue food deliveries in September.

The United Nations says as many as 3.5 million children in Pakistan are at risk from water-borne diseases, warning of a "second wave of death" from the floods.

U.N. humanitarian spokesman Maurizio Giuliano said Monday as many as six million people face the risk of contracting diarrhea, dysentery and other illnesses if donors do not provide more aid.

Some information for this report was provided by AFP.