The United States is unable to properly monitor hundreds of millions of dollars of aid it sends to western Pakistan, where al Qaeda and other extremists are extremely active, according to a new report.

Investigators for the General Accounting Office, the watchdog agency funded by the U.S. Congress, blames difficulties in tracking the aid on both security problems and insufficient cooperation by the Pakistan government.

The report focused on the problems tracking $750 million in aid for the so-called Federally Administered Tribal Areas, FATA, along the Afghanistan border. The United States last year pledged an additional $7.5 billion for Pakistan over the next five years - making aid accountability even more important.

The U.S. aid to western Pakistan includes a wide range of projects, from roads and bridges to health programs for women and children to community programs to provide, education, jobs and training.

"The FATA is an area of great strategic interest for the United Sates and Pakistan, and because the Enhanced Partnership with Pakistan Act of 2009 authorizes $7.5 billion in new nonmilitary assistance to Pakistan, accountability for development efforts there takes on particular importance," the GOA report says

"The United States continues to face security and access to Pakistani government document challenges that make monitoring of projects difficult," the GAO report says. "Without addressing gaps in planning, performance, and monitoring documentation, the U.S. government cannot fully and accurately assess the status of current assistance efforts or accountability of funds associated with U.S. development efforts in the FATA."

The administrator of the U.S. Agency for International Development, Dr. Rajiv Shah, said Friday in a briefing with journalists at the State Department that he was aware of the report and of the problems. Shah had just returned from a trip to Pakistan and Afghanistan.

"We generally concur with the report's findings and believe we can be more effective putting in place mechanisms that allow us to track and monitor resources," Shah said.

The USAID administrator said some projects had been delayed to make sure that aid was properly spent and monitored. And he said his visit had shown how security concerns made oversight dangerous and even impossible.

"There are a couple of observations had from the trip that I don't think were reflected in the report. One is the security situation there does make it harder, and we just have to recognize this, for either our own staff or more likely local partners to be out there visiting and monitoring," Shah said.

"We know we have to do that and our staff is eager to do it but it put them at great risk and you've seen what's happened in the past few weeks, with Peshawar and some of the unfortunate incidents," he said. Militants attacked the U.S. consulate in Peshawar, the capital of Pakistan's North West Province and the administrative center for the FATA, earlier this month with a truck bomb and rockets.

Shah was asked if he could reassure American taxpayers that aid money for Pakistan would be well spent." It is going to be very important – and the report highlights why it is so important – to make sure we have a financial disbursement mechanism that is clear and transparent and allows for that kind of monitoring," Shah said.

– From CNN's Charley Keyes