*Senate unable to agree on temporary funding, government shutdown hours away

*Democrats push for health benefits extension amid shutdown threat

*Trump threatens 'irreversible' federal workforce layoffs in shutdown

(Updates with Thune confirming another vote on Wednesday, adds quotes from Democratic Senators Schumer and Masto)

By Richard Cowan, David Morgan, Nolan D. McCaskill, Andy Sullivan and Bo Erickson

WASHINGTON, Sept 30 (Reuters) - The U.S. lurched toward a government shutdown on Tuesday as a vote to extend funding past a midnight deadline failed in the U.S. Senate and President Donald Trump threatened to extend his purge of the federal workforce.

The 55-to-45 vote in the Senate, falling short of the 60 votes needed to advance the legislation, all but ensured that U.S. governme

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