McConnell’s announcement amounted to another setback for GOP efforts, promoted by President Donald Trump, to repeal and replace “Obamacare” after years of promises. McConnell issued his statement not long after McCain’s office disclosed that he had undergone surgery to remove a blood clot from above his left eye, and had been advised by his doctors to stay in Arizona next week to recover.

With McConnell’s health care legislation already hanging by a thread in the Senate with no votes to spare, McCain’s absence meant it would become impossible for the majority leader to round up the votes needed to move forward with the bill next week as planned.

“While John is recovering, the Senate will continue our work on legislative items and nominations, and will defer consideration of the Better Care Act,” said McConnell, R-Ky. He did not say when he would aim to return to the health care bill.

Even before Saturday night’s developments, the fate of the health care legislation looked deeply uncertain in the Senate. In addition to two announced GOP “no” votes from moderate Susan Collins of Maine and conservative Rand Paul of Kentucky, there were at least a half-dozen other Republican senators who were withholding support from or expressing reservations about the bill McConnell released Thursday.

Last month McConnell had to cancel a vote on a previous version of the legislation as GOP opposition left its defeat assured. In a Senate divided 52-48 between Republicans and Democrats, McConnell can lose no more than two votes and still prevail.

The Senate bill, like legislation passed earlier by the House, repeals mandates requiring individuals to carry insurance and businesses to offer it, and unravels an expansion of the Medicaid program for the poor and disabled enacted under President Barack Obama’s law. Analyses of the earlier version of the Senate bill found it would results in more than 20 million additional uninsured Americans over a decade compared to current law.

The newest version attempts to attract conservative support by allowing insurers to offer skimpy plans alongside more robust ones, but also reaches out to moderates by adding billions in help for the opioid crisis and to defray high costs for consumers.

With the vote set for the coming week now indefinitely postponed, GOP success in its long-promised Obamacare repeal grows all the more uncertain, despite heavy lobbying in recent days by Trump administration officials. Democrats are unanimously opposed as are the nation’s major medical groups and insurers.

In Phoenix, Mayo Clinic Hospital doctors said McCain underwent a “minimally invasive” procedure to remove the nearly 2-inch (5-centimeter) clot and that the surgery went “very well,” a hospital statement said. McCain was reported to be resting comfortably at his home in Arizona.

Pathology reports on the clot were expected in the next several days.

McCain, 80, is a three-time survivor of melanoma. Records of his medical exams released in 2008 when he was the GOP candidate for president showed that he has had precancerous skin lesions removed and had an early stage squamous cell carcinoma, an easily cured skin cancer, removed.

He was re-elected in November to a sixth Senate term.