WASHINGTON (December 3, 2012)—The House Republicans negotiating with President Barack Obama in hopes of avoiding a plunge over the so-called fiscal cliff were proposing Monday to increase the eligibility age for Medicare and to lower cost-of-living hikes in Social Security benefits.

The proposal is a response to Mr. Obama's offer last week to hike taxes by $1.6 trillion over the coming decade, but to exempt Medicare and Social Security from cuts to beneficiaries.

The GOP plan also proposes to raise $800 billion in higher tax revenue over the decade, but would keep the Bush-era tax cuts - including those for wealthier earners being targeted by Mr. Obama in place for now.

U.S. House Speaker John Boehner said the GOP proposal is a "credible plan" for Mr. Obama and that he hopes the administration would "respond in a timely and responsible way."