Many of the Pakistani-Americans who live in ethnically diverse Jackson Heights, Queens, are saddened by the flooding in their homeland and even have relatives among the displaced.

But, despite family ties, many aren't giving to the relief effort because they simply don't trust the Pakistani government.

“The money might reach a quarter of the people who really need it,” says Mussarat Khan as he leaves a doctor’s office. “The doctor and I were discussing the flood, there is just so much corruption.”

Whether the corruption allegations are true or not, perceptions that money would be wasted is one reason relief organizations say contributions for flood victims are way down.

“There has been a tepid response, it is down significantly from other disasters of recent times,” says Ken Berger, president of Charity Navigator, a Glen Rock, N.J., evaluator of charities. “There could be a host of different reasons – from donor fatigue to people not feeling comfortable because of their concerns about terrorism."

Mr. Berger says some of the problem could be related to the difficulty of media reaching the flooded areas. But, he says, giving could also be down because people are on summer vacation or simply because of the vast geographical distance between the US and Pakistan.

Although some people may not give because of their concerns about corruption, he says those same concerns existed for Haiti, where contributions after January's earthquake far outpaced the rate of giving in the aftermath of Pakistan’s flooding.

Whatever the reason, charities are feeling the affect.

At the Zakat Foundation of America in Chicago, Executive Director Halil Demir says giving has been “very slow,” with the charity not even raising 20 percent of what it raised to help Haitians. “This is very scary that the message is not getting through.”

It’s a similar situation at Concern Worldwide, a nonprofit that responds to such crisis, says Dominic MacSorley, the operations director.

“We are trying to reach 250,000 people and we have pledges of $8 million but our budget needs to double and double next week,” he says.

On Thursday, the slow giving is one reason why Hillary Clinton will visit the United Nations for a General Assembly plenary session on the humanitarian situation in Pakistan. Last week, the UN appealed for pledges of $460 million. The US responded with a pledge of $90 million but other nations have been slower, says Mr. MacSorley.

For example, MacSorely says 10 days after the earthquake hit Haiti, there were pledges equal to $495 for each person affected by the disaster. So far, he says there have been pledges of $3 for each person affected by the flooding.

The lack of response by international donors is perplexing, says Rabiah Ahmed, a spokeswoman for the Islamic Relief, the largest Muslim charity.

“In the past there was a lot more media coverage, more government officials and celebrities organizing benefits for those in need,” she says. “We don’t see that now.”

Islamic Relief has raised $2 million in cash and $22 million in donations of food, water, and clothing. But, the charity has now increased its appeal to raise $4 million.

“Our supporters have to dig deep,” says Ms. Ahmed, who adds that this is now the religious period of Ramadan, a time of giving.

Some of that money will come through grass-roots efforts such as one in Plainfield, Ind., where a local mosque will ask its members to give money for flood relief during an Iftar dinner. Iftar is the meal after the day-long Ramadan fast.

Some organizations are hopeful that in the next few days the pace of giving will pick up. For example, the Islamic Medical Association of North America (IMANA), which sent six doctors to Pakistan Aug. 14, is sending its members e-mails and appealing on its Facebook page for contributions. By Friday it also plans an appeal on ARY, a Dubai-based digital television station watched by many Pakistanis.

“When people donate to us, all the money goes to medical relief,” says Abida Haque, IMANA president in Houston. “Our physicians all travel at their own expense.”

She says there is a desperate need to vaccinate children, to treat wounds, and provide potable drinking water.

Organizations such as IMAMA, however, will have to win over people like Syed Irshad Bukhari, a Pakistani-American news dealer in Manhattan and Rizwan Hamid, manager of a restaurant in Queens.

Mr. Bukhari recalls giving money for earthquake relief in Pakistan and finding out corrupt officials took a generous amount for themselves. Now, he says, “If you are going to give help, you give it directly to relatives.”

And Mr. Hamid says he would give to only Humanity First, a charity that he knows and trusts. But, so far, he says he hasn’t given. Instead, if he knows a family that needs help, he would prefer to give them money directly.