Votes came as premium tax credits for estimated 21.8 million enrollees of plans set to expire at end of month

The US Senate on Thursday rejected competing proposals to address the imminent expiration of subsidies for Affordable Care Act health insurance plans, greatly increasing the chances that healthcare costs will soon rise to unaffordable levels for millions of Americans.

The votes, part of a deal brokered between Republican majority leader John Thune and the Democratic senators who agreed to reopen the government after a historically long shutdown last month, came as premium tax credits for an estimated 21.8 million enrollees of the plans are set to expire at the end of the month. Health policy research group KFF estimates that annual premiums will more than double if the subsidies are allowed to expire.