Former Federal Reserve Chairman Alan Greenspan said the recent rise in Treasury yields represents a “canary in the mine” that may signal further gains in interest rates... Higher yields reflect investor concerns over "this huge overhang of federal debt which we have never seen before," Greenspan said... "I’m very much concerned about the fiscal situation... [An increase in interest rates would] make the housing recovery very difficult to implement and put a dampening on capital investment as well."...The U.S. budget deficit reached a record $1.4 trillion for the fiscal year that ended Sept. 30 amid falling tax revenue from the recession, a bailout of the banking and auto industries, and the $787 billion economic stimulus package."I don’t like American politics and what’s happening," Greenspan said... Historically, there has been "a large buffer between the level of our federal debt and our capacity to borrow... That’s narrowing. And I’m finding it very difficult to look into the future and not worry about that."