President Obama is hiding the truth when it comes to the nation's overspending and long-term debt problems, a key Republican senator said Monday.

Senate Budget Committee ranking member Jeff Sessions (Ala.) faulted the president's proposal, which is set to be released later Monday morning, for not addressing bloated entitlement programs and not cutting enough federal spending while raising taxes.

"I believe what Erskine Bowles, who President Obama named to head his fiscal commission, said yesterday, which is that this budget is nowhere close to avoiding this fiscal crisis this nation is facing," Sessions said on Fox News. "The president has not told us the truth."

Sessions's comments are another sign that Obama's budget plan will face immediate pushback from Republicans in Congress, who are under pressure from their base to seek more drastic measures to cut spending and address the national debt. 

The president's plan would spend $3.7 trillion while reducing budget deficits by $1.1 trillion over 10 years. But the plan does not tackle spending in programs such as Medicare, Medicaid and Social Security, which are mainly responsible for the country's gaping deficits.

"This is a tough budget," White House budget director Jack Lew said Monday morning on CNN. "It's a budget that takes $400 billion out of discretionary spending by freezing it over the next five years. And that means making the kinds of trade-offs where it's no longer just cutting things that we would call waste or fraud or abuse ... Like every American family, we have to live within our means and invest in the future."

Republicans have noted that the plan falls short of the president's fiscal panel's proposal, which would have cut $4 trillion from the deficit over 10 years.

"For Mr. Lew to suggest we will be living within our means within the 10 years this budget covers is totally wrong," Sessions replied. "We have no plan in this budget to pay down debt or come close."