WASHINGTON — While Lamar Alexander, R-Tenn., says he sides with President Donald Trump on the need to repeal and replace the Affordable Care Act, but says the 350,000 Tennesseans who rely on the federal exchange to purchase health care coverage cannot afford to wait two years on a replacement plan.

Alexander, the Volunteer State's senior senator, said he joined a few other Republicans in the U.S. Senate by voting against the amendment to repeal Obamacare without a replacement plan.

"I agree with President Trump that we should repeal and replace major parts of the Affordable Care Act at the same time," Alexander said. But, he added, waiting two years for a replacement plan is not the proper way forward."

Alexander is also among the moderate Republican senators who have balked at the number of Americans who would lose insurance coverage due to cuts to Medicaid and other measures.

"I don't think Tennesseans would be comfortable canceling insurance for 22 million Americans and trusting Congress to find a replacement in two years," he said. "Pilots like to know where they're going to land when they take off, and we should too."

Even as Alexander was releasing a statement on his Obamacare stance, fellow Tennessee Republican Bob Corker announced he intended to vote for an amendment to repeal core elements of Obamacare.

Corker, who was one of nine Republicans in the Senate to vote against a different repeal-and-replace plan a day earlier, said Wednesday that he was taking a stance opposite Alexander's — repeal core elements of Obamacare now, while allowing for a reasonable transition period for a replacement to be developed and implemented.

"As I have said before, I believe the best path forward is for Congress to repeal Obamacare after a reasonable transition period," Corker said. "This amendment would take us back to a level playing field where, by a date certain, all sides have incentive to work together to develop a health care replacement that would generate broad support and stand the test of time."

Ultimately, the Senate voted 45-55 to reject the repeal-and-replace amendment on Wednesday. Alexander was one of seven Republicans to join Democrats in rejecting the measure.

Wednesday's measure was identical to a measure narrowly passed by Republicans in 2015, when only one GOP senator — Maine's Susan Collins — voted against it. Obama vetoed the vote two years ago.

Alexander explained his change of heart by saying that Obamacare is closer to complete failure and a replacement plan is needed now.

"In 2015, we could have waited two years for relief, but we cannot now, when Tennessee insurance commissioner Julie McPeak says the state's individual insurance market is 'very near collapse,'" Alexander said. "We have 350,000 Tennesseans who buy insurance in the individual market — songwriters, small businessmen and women, farmers — who are worried today that they may have zero options for insurance in just six months."

Tuesday's bill, which Alexander voted for but Corker opposed, would have repealed Obamacare and replaced it immediately.

Senate Republicans are attempting to find a way to get to a majority vote on a partial repeal of Obamacare, in order to jump-start negotiations with the House of Representatives, where the finer details of a repeal plan can be ironed out.