The federal government's rescue plan comes with a very high price tag for American taxpayers. Ken Rogoff says they will be left facing a $1 trillion deficit — if not double that figure.

"I can't imagine this crisis is going to end up costing the government less than 6 to 7 percent of GDP," the former chief economist of the International Monetary Fund told the Financial Times.

Even before the rescue plan was announced, the United States faced a $438 billion federal deficit in 2009, or 3 percent of gross domestic product, according to the Congressional Budget Office.

According to the Financial Times, the $700 billion mortgage securities rescue fund is authorized for two years, but even if it's not all spent in the first year, the federal deficit would easily top $1 trillion next year.

"Were the financial crisis to end today, the costs would be painful but manageable, roughly equivalent to the cost of another year in Iraq," Rogoff wrote in an op-ed for the newspaper.

Interestingly, economist Nouriel Roubini's estimate of the total private credit losses from the crisis, that is, what the banks must write down — lines up more or less exactly with Rogoff's taxpayer cost assessment.

The former Clinton White House economist recently estimated the financial crisis will lead to credit losses of at least $1 trillion and most likely will be closer to $2 trillion.