Is US national debt nearing the danger zone?

From Dailyfinance.com

Krugman said the key statistic remains the national debt as a percent of U.S. GDP. Large budget deficits -- even deficits above $1 trillion for consecutive years -- are needed, short-term, to help create demand and pull the U.S. economy out of its pronounced recession.

Long-term, Krugman underscored that the national debt can become a problem, but the United States, with a national debt totaling about 60-65 percent of GDP, is nowhere near levels approaching the "danger zone." For example, Japan ran a national debt equal to 100 percent of GDP in the 1990s, Krugman said.

Krugman also reiterated Sunday his support for a second, major fiscal stimulus package -- one he believes will be needed to fill the large demand hole created by the recession.