The United Nations says it needs far more money than has been donated to assist the millions of Pakistanis who remain in dire need from the country's worst flooding in history.

The U.N. announced on Monday that it is preparing to double its initial $460 million appeal, which is currently about 70 percent funded. Private donations have brought the total amount of current aid to about $1 billion.

The additional money will go to provide food, water, shelter and medicine for some 8 million Pakistanis who are in need of daily assistance after being displaced by the floods.

"We still have millions of people out of their" houses, U.N. envoy Jean-Maurice Ripert told CNN. "We have hundreds of thousands of people that we have to feed, take care of on a daily basis."

Almost 20 million people have been affected by the floods in Pakistan, which began in late July and have engulfed a 600-mile stretch of land, nearly the size of Italy, down the center of the country.

Some 1,800 people have died so far and 4 million left homeless. Unsanitary conditions and continuing harsh weather have threatened the loss of more life.

Especially vulnerable are an estimated half a million infants who are expected to be born in the next six months, according to the U.N.

"If we don't scale up our nutrition activities, the lives of thousands of children are at risk", said Stefano Savi, head of the UNICEF office in Balochistan's provincial capital Quetta.

Meanwhile, news agencies have reported that some Pakistani Christians have been pressured to convert to Islam or risk being denied humanitarian assistance.

Fides News has compiled testimonies of several Pakistani Christians, including Abid Masih, who said, "My wife is sick, but the doctor refused to visit her and treat her, saying that we should wait for the World Health Organization to send Christian doctors."

Carl Moeller, president of Open Doors U.S.A., denounced the discrimination saying, "You can imagine that terrible choice: either you abandon your faith or you cannot feed your child."

The Christian population in Pakistan numbers about 2.8 million, while the rest of the country is mostly Sunni Muslim.

For the last eight years, the United States Commission on International Religious Freedom (USCIRF) has listed Pakistan as a "country of particular concern" for its discrimination against Christians and other religious minorities, although the U.S. Department of State has not followed that recommendation.