Senate Republicans circulated a sweeping plan to drive down the cost of mortgages by expanding the federal government's role in the industry, officials said on Monday night as debate opened on an economic stimulus bill at the top of President Barack Obama's agenda.

The emerging proposal also relies on a bigger and more widely available tax break for homebuyers than is now available, those officials added as Senate Republicans staked their claim to a different type of economic recovery measure than Democrats and the administration favor.