WASHINGTON — Divided government’s increasingly urgent drive to prevent a Treasury default and end a 15-day partial government shutdown took a highly partisan turn today as House Republicans unveiled a proposal stocked with conservative priorities that the White House instantly rejected.

It was unclear whether House Speaker John Boehner and the GOP leadership had the votes to pass their measure, or whether it would even be brought to the House floor for a vote. Even so, the immediate result was to freeze Senate negotiations on a bipartisan compromise that had appeared ready to bear fruit.

As a day of secret meetings and frenzied maneuvering unfolded, Sen. Barbara Mikulski, D-Md., stood on the Senate floor at midafternoon and declared, “We are 33 hours away from becoming a deadbeat nation, not paying its bills to its own people and other creditors.”

The events prompted an outbreak of partisan rhetoric, mixed with urgent warnings that both the U.S. and global economies could suffer severe damage quickly unless Congress acted by Thursday.