Lindsey Graham. Alex Wong/Getty Images Sen. Lindsey Graham responded Friday to Sen. John McCain's announcement that he would vote against the Graham-Cassidy healthcare proposal set to come before the Senate for a vote next week.

McCain, an Arizona Republican, dealt a critical blow to the bill with his announcement. Without McCain's "yes" vote, Republicans are virtually assured they will not reach the 50 votes necessary to pass the legislation.

Graham, the bill's sponsor, and McCain share one of the closest friendships in Congress.

"My friendship with John McCain is not based on how he votes but respect for how he’s lived his life and the person he is," Graham, a South Carolina Republican, said in a Friday statement. "I respectfully disagree with his position not to proceed forward on Graham-Cassidy-Heller-Johnson. I know Graham-Cassidy-Heller-Johnson is the best chance to repeal and replace Obamacare."

"Obamacare is collapsing in Arizona, South Carolina, and across the nation — driving up premiums and reducing choices," he continued. "I feel an obligation to fix this disaster and intend to push forward for state-centric health care versus Washington-knows-best health care. "I’m completely convinced taking money and power out of Washington and returning it to states to administer health care is the best way to replace a collapsing Obamacare system. I’m excited about solutions we have found in Graham-Cassidy-Heller-Johnson. We press on."

Earlier Friday, McCain said Republicans "should not be content to pass healthcare legislation on a party-line basis."

"I cannot in good conscience vote for the Graham-Cassidy proposal," he said. "I believe we could do better working together, Republicans and Democrats, and have not yet really tried. Nor could I support it without knowing how much it will cost, how it will effect insurance premiums, and how many people will be helped or hurt by it. Without a full CBO score, which won’t be available by the end of the month, we won’t have reliable answers to any of those questions."

"I take no pleasure in announcing my opposition," he continued. "Far from it. The bill’s authors are my dear friends, and I think the world of them. I know they are acting consistently with their beliefs and sense of what is best for the country. So am I. I hope that in the months ahead, we can join with colleagues on both sides of the aisle to arrive at a compromise solution that is acceptable to most of us, and serves the interests of Americans as best we can."