WASHINGTON — Top Republicans and President Barack Obama are lining up behind a modest but hard-won bipartisan budget agreement that seeks to replace a portion of tough spending cuts facing the Pentagon and domestic agencies.

The deal to ease those cuts for two years is aimed less at chipping away at the nation’s $17 trillion national debt than it is at trying to help a dysfunctional Capitol stop lurching from crisis to crisis.

It would set the stage for action in January on a $1 trillion-plus spending bill for the current budget year.

The measure unveiled by House Budget Committee Chairman Paul Ryan and Senate counterpart Patty Murray of Washington blends $85 billion in spending cuts and fees to replace $63 billion in cuts to agency budgets over the coming two years.