WASHINGTON (Reuters) - The Senate on Thursday, as expected, defeated a Republican plan for replacing $85 billion in across-the-board federal spending cuts called "sequestration," which are set to begin within hours.

The Republican proposal would have given President Barack Obama two weeks to come up with more targeted spending cuts than the indiscriminate deficit reductions that are set to hit most government agencies. Democrats opposed it largely because they want tax increases to be included in new deficit-reduction efforts.

The Senate is also expected to defeat a competing Democratic proposal for heading off the indiscriminate spending cuts.

(Reporting By Richard Cowan; editing by Christopher Wilson)