The committee responsible for finding a plan to cut the U.S. deficit by at least $1.2 trillion asked the congressional budget chief hard-hitting questions about the government's discretionary spending, spurring further debate Wednesday.

Congressional Budget Office Director Douglas Elmendorf told members of the Joint Select Committee on Deficit Reduction -- commonly referred to as the supercommittee -- the funding Congress is authorized to spend is at its lowest level as a percentage of gross domestic product since 2002.

However, the actual spending of the federal funds as percentage of GDP is at the highest level in about 20 years, totaling $1.35 trillion, or roughly 40 percent of overall federal spending in 2011.

These aren't answers the supercommittee wanted to hear. One day after a private meeting and less than a month until the Nov. 23 deadline to agree on a plan for the president and both houses of Congress, the 12 committee members are struggling to find a bipartisan solution.

Committee co-chairman Rep. Jeb Hensarling, R-Texas, questioned Elmendorf on the CBO's numbers regarding what Hensarling called "huge run-ups in discretionary spending since (U.S. President Barack) Obama came into office."

As an example, Hensarling pointed out the CBO reported the U.S. Commerce Department's discretionary spending went up 219 percent with the stimulus program. It would have gone up 108 percent without the stimulus program, CBO data indicate.

Hensarling's statements to Elmendorf represent prevailing Republican sentiment that further cuts should be made to discretionary spending.

Democrats on the committee begged to differ, highlighting the ongoing partisan political climate in Washington. While supercommittee co-chairwoman Sen. Patty Murray, D-Wash., said members are working "very hard" to find common ground, she made it clear Democrats oppose further cuts in optional federal spending.

"It doesn't make sense to simply keep slashing at one small part of the budget that disproportionately affects middle-class families and the most vulnerable Americans," Murray said, referring to the discretionary funds Congress must renew each year.

Elmendorf, who has been CBO director since January 2009, said Congress has indeed made significant efforts to reduce discretionary spending, half of which goes for defense.

But he also told the supercommittee the legislation it comes up with, if any, could directly alter the path of such spending, the remainder of which goes for education, transportation, housing assistance, veterans' benefits, public health, international affairs and a variety of other federal programs and activities.

Unlike mandatory spending that includes entitlement programs such as healthcare and welfare, discretionary federal spending is optional. Thus, it is a ripe target for inevitable budget cuts as the supercommittee continues to deliberate its plan to reduce the deficit.