Washington (CNN) -- State Department officials are acknowledging that the world economic situation has had an impact on the ability of many governments to help flood-ravaged Pakistan cope with that country's worst disaster in 80 years.
"There's no question ... that the world economic situation, as a general matter, has had an impact on the ability of many governments around the world to give and give generously," Assistant Secretary of State Eric Schwartz told reporters at a press briefing Wednesday.
Schwartz said that despite less than optimal economic circumstances, "donor governments continue to make humanitarian response a very high priority."
"Donor fatigue is an issue, but I think it's not an issue for the United States," said Schwartz.
Schwartz said that when catastrophic events such as the Pakistani flooding occur, the U.S. will contribute "more or less ... a quarter of the response in the humanitarian disaster."
"That ability to do so and put money on the table has a catalytic effect, and brings other (governments) forward," said Schwartz.
Frank Ruggiero, deputy special representative for Afghanistan and Pakistan, said that the international community has responded to the flooding in Pakistan, but will have to provide more support to the Pakistani government to help mitigate the disaster.
"As we see the flooding worsen over the coming weeks, I think the international community will need to provide even more additional assistance," said Ruggiero. "The need is extreme at this point."
State Department spokesman P.J. Crowley said, "I think you will see the response pick up as people understand the magnitude of this."
The officials also addressed concerns about U.S. aid not arriving quickly enough to help victims.
Ruggiero explained that bridges in flood-affected Pakistani areas are out, making it hard to reach victims. But he stressed that the United States has been there from the start of the crisis.
"U.S. helicopters were flown from Afghanistan to Pakistan to help save people that were stranded by the flooding and to deliver humanitarian supplies," said Ruggiero.
"U.S. C-130s from Afghanistan have done the same thing," said Ruggiero, referring to military transport planes. "On the civilian assistance side, we have provided $90 million of U.S. assistance."
Mark Ward, acting director of the U.S. Agency for International Development (USAID) office of foreign disaster assistance, said, "We're doing all we can right now" to help the Pakistani government respond better.
"We send in water filtration units," said Ward. "We send in rescue boats. We send in thousands of rolls of plastic sheeting that people can use to make temporary shelter when they go back to the villages that they had to evacuate."
Ward said USAID is coordinating efforts with the U.S. military .
"The military is bringing in airlift support and halal (prepared under Islamic dietary laws) meals and some bridges, and we're complementing that as best we can from our warehouses around the world," said Ward.
Responding to questions about reports of corruption among some aid groups that have received donations, Ward said that those non-governmental organizations that the U.S. endorses have been carefully vetted.
"There is a process that we go through before an organization can receive funds from the United States government -- and it's a tough process. And any Pakistani NGO that qualifies for a grant has also gone through that process," said Ward.
Ward added that "anybody who wants to give a private donation for Pakistan relief should feel very comfortable in giving to one of those organizations" listed on the State Department's website.