WASHINGTON – Senate Republicans fashioning next year’s $2.6 trillion budget are running into a familiar problem – balky moderates reluctant to worsen record federal deficits with a fresh round of tax cuts.

President Bush has proposed $100 billion in tax cuts for the next five years. Under pressure from moderate GOP senators, Senate Budget Committee Chairman Judd Gregg, R-N.H., planned to start debate in his panel Wednesday on a fiscal plan focused on only about $70 billion in tax cuts over the next five years, said Senate aides speaking on condition of anonymity.

House Budget Committee Chairman Jim Nussle, R-Iowa, will try pushing a fiscal outline through his committee Wednesday centered on less than $50 billion in tax reductions, said congressional aides. These aides said House GOP leaders hope to eventually enact additional tax cuts this year.

For the first time since 1997, both chambers’ budgets will also order billions in savings from automatically paid benefits like Medicaid, the federal-state health program for the poor and disabled.

Besides limiting the amount of tax cuts, the centrists want the budget to require that any new tax reductions be paid for by raising other taxes or cutting spending – something Gregg and most Republicans have resisted. The same demand by moderates produced an embarrassing stalemate last year that left the GOP short of the Senate votes it needed to enact a budget.

“It’s a question of how we deal with all the issues in an equitable fashion,” said Sen. Olympia Snowe, R-Maine, referring to Bush’s proposals for tax cuts and “major reductions in domestic programs.”

Both budget committees’ plans highlight the continued clout wielded by a handful of Senate moderates, despite their diminished leverage. Republicans have expanded their 51-48-1 Senate majority of last year – the independent leaned Democratic – to 55-44-1 this year.

Besides Snowe, last year’s holdouts were moderate Sens. Susan Collins, R-Maine, Lincoln Chafee, R-R.I., and John McCain, R-Ariz.