ATHENS, Greece — Greece finally met a deadline that counted on Thursday, delivering a series of sweeping proposals to its creditors before midnight to set off a mad rush toward a weekend deal to stave off a financial collapse of the nation. The package of reforms raised hopes that Greece can get a rescue deal that will prevent a catastrophic exit from the euro after key creditors said they were open to discussing how to ease the country's debt load, a long-time sticking point in their talks. In a significant about-face, the government caved into demands for a new round of austerity measures, including sales tax hikes and cuts in state spending for pensions that the left-leaning Greek government had long resisted. In the text of proposals sent by Athens late Thursday, the government conceded to demands it had previously refused to accept — mostly on moving various categories of goods and services to higher sales tax rates — in exchange for a new 53.5 billion-euro ($59 billion) bailout package. Many of the proposed reforms were harsher than those roundly rejected by the Greek public in a bailout referendum last Sunday.