WASHINGTON — There is still $60 billion in taxpayer-funded, bank bailout funds available to be spent on housing and other programs, a top watchdog for the government’s Troubled Asset Relief Program said Thursday.

“”TARP’s financial outlook is improving, with more institutions repaying TARP and cost estimates continuing to decline,”” the Office of the Special Inspector General for the Troubled Asset Relief Program said in its quarterly report to Congress. “”Nevertheless, it bears repeating that Treasury’s ultimate return on its TARP investments depends on many variables that are largely unknowable at this time.””

It pointed out that as of March 31, about $146.8 billion in TARP funds were still outstanding.

The report noted that costs will vary depending on the Treasury’s ability to sell certain securities in troubled insurer American International Group Inc. and the ability of many banks to repay. It adds that more than 550 mostly small banks have yet to repay their TARP funds.

It added that uncertainties about the cost of TARP will also depend on the fund’s housing programs, such as a $7.5 billion program for 18 of the hardest-hit U.S. states to create programs for housing rehabilitation, help for unemployed homeowners and troubled borrowers who owe more than their home is worth.

Another housing program, the Home Affordable Modification Program, has allocated $30 billion to modify mortgages for troubled homeowners. So far roughly $1 billion has been spent and roughly 630,000 loans modified, against a target of 3 to 4 million.

The report added that TARP has pledged $22.4 billion for its Public-Private Investment Program, which employs private equity and matching government funds to buy distressed mortgage securities. The program, which is scheduled to last at least seven more years, has drawn down $16 billion in debt and equity financing from Treasury funding out of the total obligation as of March 31, of which $840.5 million has been repaid.