Bipartisan budget experts foresee a grim future for America if nothing is done to stifle the nation's budget deficit.

It currently stands at about $500 billion and is expected to top $1 trillion in the next 10 years.

Sen. Rob Portman says even that estimate paints a rosy picture of the future.

"It assumes no wars, it assumes no recessions," the Ohio Republican explained. "It assumes no terrorist attacks, it assumes interest rates are going to stay at relatively low rates."

Portman and Rep. Chris Van Hollen, D-Maryland, laid out what they feel are the biggest challenges facing the nation's growing budget problem.

"Entitlement spending is set to double over the next decade. It will consume almost 100 percent of all tax revenues within the decade," Portman said.

And Van Hollen sees an immediate problem in the Highway Trust Fund set to expire at the end of this summer.

"This is threatening thousands of construction jobs around the country," he said.