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The national debt has reached an all-time high of $16 trillion, according to the Treasury Department.

The new debt figures came out just hours before the three-day Democratic National Convention kicked off in Charlotte, N.C., fueling new GOP attacks against President Obama and his spending policies.

"Today's news is another sad reminder of President Obama's broken promise to cut the deficit in half," said House Speaker John Boehner, R-Ohio, in a statement today. "This debt is a drain on our economy and a crushing burden on our kids and grandkids, and it's yet another indication that the president's policies have made things worse."

It appears the U.S. first reached the new $16 trillion debt figure last week, on Aug. 31, according to the Daily Treasury Statement. The Treasury Department quietly posted it on its website today.

The new debt numbers work out to about $51,000 for every American, according to U.S. Census population estimates.

Out on the campaign trail in Cedar Rapids, Iowa, Rep. Paul Ryan today called the new debt figure a serious threat to jobs and the economy.

"Of all the broken promises from President Obama, this is probably the worst one because this debt is threatening jobs today," he said. "It is threatening prosperity today, and it is guaranteeing that our children and grandchildren get a diminished future."

The Republican National Committee was quick to seize on the debt news, going on the attack with a new online ad.

The one-minute ad shows three clips of the president speaking about the national debt, overlaid rising debt numbers. It hits Obama for his remarks on the campaign trail in 2008, when the debt first topped $9 trillion, as well as his February 2009 announcement at a "Fiscal Responsibility Summit" that he planned to cut the deficit in half by the end of his first term.

"By his own measurement, President Obama has failed," the ad says at the end. "Talk is cheap. Our debt isn't."

Republicans have made the debt a major issue this election cycle, installing two large debt clocks as centerpieces of their convention last week in Tampa, Fla.

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House Majority Leader Eric Cantor said today the national debt has increased more than $5 trillion during the president's first term. He added that the president's proposed tax on small business owners could mean 700,000 lost job opportunities.

"It's time to address the serious fiscal challenges we face and stop spending money we don't have," he said in a statement today. "We cannot afford more of the same failed policies, big-government spending and massive tax hikes on hardworking families and small businesses."

Rep. Tom Graves, R-Ga., today called the debt "untenable, irresponsible, and unsustainable."

"Clearly, the President's vision for America is one of debt and dependency, rather than opportunity and prosperity," he said in a statement. "Instead of spending our way into oblivion and increasing our ever-growing debt, we must begin the process to restoring our fiscal health through growing the economy."

ABC's Shushannah Walshe contributed to this report.