DEMOCRATS CONTROLLING THE US Senate are planning to try to pass a stand-alone measure to increase the government’s borrowing cap, challenging Republicans to a filibuster showdown that could unnerve financial markets as the deadline to a first-ever default on U.S. obligations draws closer.

A spokesman said Senate Majority Leader Harry Reid could unveil the measure as early as today, setting the table for a test vote later in the week.

The measure is expected to provide enough borrowing room to last beyond next year’s election, which means it likely will permit $1 trillion or more in new borrowing above the current $16.7 trillion debt ceiling that the administration says will be hit on 17 October.

The development came as a partial shut down of the government enters its second week with no end in sight.

It’s not clear whether Reid’s gambit will work, but Republicans are expected to oppose the measure if it doesn’t contain budget cuts to make a dent in deficits.

The question is whether Republicans will filibuster the measure.

Until recently, debt limit increases have not been the target of filibusters; the first in memory came four years ago, when Democrats controlled the Senate with a filibuster-proof 60 votes.

Many Republicans in the Senate, including Minority Leader Mitch McConnell of Kentucky and Whip John Cornyn of Texas, have voted for so-called clean debt limit increases during Republican administrations.

Some Republicans seemed wary of participating in a filibuster that could rattle the stock and bond markets.

“We shouldn’t be dismissing anything out of hand, whether it’s the debt ceiling or what we’re going to do with this government shutdown,” Senator Lisa Murkowski, R-Alaska, said.

The impasse over the shutdown — sparked by House Republicans’ insistence that a temporary funding bill contain concessions on President Barack Obama’s health care law — shows no signs of breaking, as each side sticks to its guns and repeats its talking points.

Democrats from Obama on down to the most junior lawmakers said again that the House should vote immediately on ending the partial closure of the government.

Obama said House Speaker John Boehner, “doesn’t apparently want to see the … shutdown end at the moment, unless he’s able to extract concessions that don’t have anything to do with the budget.”

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