Bank of America Corp said on Tuesday the pace of its mortgage modifications under the government's primary aid program to forestall foreclosures continued to slow in August.

BofA completed 3,600 permanent mortgage modifications in August under the U.S. government's Home Affordable Modification Program, or HAMP. That is the lender's fewest conversions from trial to permanent modifications in a month under the program, which began at the start of 2010.

By contrast, about 10,000 borrowers received modifications under Bank of America's private mortgage program in August, bringing the total to roughly 600,000 borrowers since January 2008.

Since January, BofA has completed 79,800 modifications under HAMP. The program, overseen by the U.S. Treasury, provides incentives for banks to modify borrowers' mortgages to avoid foreclosure.

The Home Affordable Modification Program was implemented as the federal government's primary effort to stem the increase in American home seizures from delinquent borrowers.

Homeowners receive three-month trial modifications of their loans from the bank. If they meet the program's requirements during that period and stay current on payments, their mortgages are then modified permanently.

But HAMP came under fire from critics who said it did not screen borrowers appropriately and did not adequately measure whether they could avoid re-defaults.

In April, the U.S. Treasury began requiring full documentation of a borrower's financial information, rather than allowing banks to accept it verbally. The government also began requiring banks to fully underwrite modifications before they approved the applicants.

The changes have slowed the number of approved modifications significantly, and allowed fewer borrowers to qualify for the trial program.

Charlotte, North Carolina-based BofA's pipeline of borrowers in trial mortgages declined in August to roughly 72,000 to 73,000, a bank spokesman said.

That figure is down about 10 percent from 84,700 mortgages modified on a trial basis in July.

The number will continue shrinking, the spokesman said, as borrowers drop out of the program and fewer new borrowers qualify. Some of those are moved into the bank's own proprietary modification program.

(Reporting by Joe Rauch; Editing by Gary Hill)