The lower value of the U.S. government's shares of General Motors Co. and American International Group will dump $21 billion more on the 2013 budget President Barack Obama released Monday.

The Obama administration said Monday the government's depreciating stock in GM and AIG forced it to revise an estimate made in August 2011. The budget boosts the net cost of the Trouble Asset Relief Program (TARP) to $67.8 billion, a stark increase from $46.8 billion.

That adds $21 billion to the Obama administration's total fiscal 2013 budget, which projects a deficit of $1.33 trillion.

The White House estimates stem, however, from Nov. 30 share prices for both GM and AIG, both of which the government bailed out in 2008 and 2009. Shares of both companies have trended upward in the two-plus months since, so the government could revise its projection later this year and reduce the deficit if the trend continues.

The tasks ahead for TARP are to recover the remaining investments in the financial sector and auto industry in a manner that continues to promote financial stability while also maximizing the return for taxpayers, the White House budget document reads.

GM entered the market with a public stock offering of $33 in November 2010, and the stock's early successes suggested the government's TARP program could see a profit from the $700 billion bailout fund. It also helped calm last year's record deficit forecast of $1.6 trillion.

But GM's stock fell nearly $10 over the next year after its original public stock offering -- and nearly $15 from its January 2011 high of $38.10 -- to its Nov. 30 share price of $23.31. This was largely due to the economic calamity in Europe and the subsequent fears of a prolonged recession in the United States.

However, GM shares have rebounded since the Nov. 30 price. As of 1 p.m. ET on Monday, GM shares were trading at $25.37, which was down 0.51 percent.

The White House's revised forecast of the TARP program comes just weeks after the Congressional Budget Office jumped its estimate by $23 billion, which it said was also mostly because of the lower values of GM and AIG shares.

In the budget and in recent weeks, Obama has touted the auto industry's dramatic turnaround as a success for his administration, amid criticism from Republican presidential front-runner Mitt Romney.

Both President George W. Bush and Obama pumped billions into GM and Chrysler in 2008 and 2009, believing it was necessary to rescue the companies from liquidation. Romney has advocated a more conventional bankruptcy approach without government intervention. Chrysler repaid all outstanding loans to the U.S government last May.

The White House said since the companies restructured and emerged from bankruptcy, the auto industry has added more than 100,000 new jobs. Sales are also up, and GM once again became the world's best-selling automaker.