WASHINGTON  A day after Senate Democrats said that they had clinched an agreement on a far-reaching overhaul of the nation’s health care system, Republicans vowed on Sunday to continue their fight while acknowledging that their chances of stopping Senate passage had faded.

Asked whether he and his fellow Republicans could yet block the bill, John McCain of Arizona seemed resigned to its passage.

“Probably not,” he replied on “Fox News Sunday.” “We’ll fight the good fight, we‘ll fight until the last vote.”

If the Senate bill passed, it would have to be reconciled in conference with the earlier House version. The two differ substantially; and a key senator said Sunday that it would be difficult for his chamber to pass anything that varies much from the Senate version.