Sen. Ben Nelson said Thursday that he will oppose the creation of a government-run health insurance plan as part of a health care overhaul, contrary to the position held by many of his fellow Democrats.

Nelson, D-Neb., said he may try to assemble a coalition of like-minded centrists opposed to the creation of a public plan, as a counterweight to Democrats pushing for it. He said he does not believe a majority of the Senate supports the idea.

Nelson plans to outline his principles for a health care overhaul in more detail in a column to be published this weekend in his hometown paper, the Omaha World-Herald. Besides opposing a public plan, Nelson said he wants to change the way health care is delivered to make it more efficient and squeeze out unnecessary costs. Those are principles broadly supported by lawmakers of both parties, though achieving them in practice is proving to be difficult.

Nelson’s announcement came the day after 16 Democratic and independent senators wrote the leaders of committees crafting an overhaul, urging them to include what supporters call a “public plan option” in the legislation. The idea, supporters say, is that by forcing private insurers to compete with a government-run plan similar to Medicare, the government can encourage insurers to provide better benefits and prices to consumers.

But Nelson sides with opponents, who say a government-run plan would undermine the nation’s existing system of employer-sponsored health insurance.

Republicans, insurers and business groups say private insurers could not compete with a government-run plan, which presumably wouldn’t have to spend money on activities such as marketing or developing networks of participating physicians and hospitals. Eventually, opponents say, most consumers would join the public plan, either because its prices are lower or because their employers stop offering insurance.

“At the end of the day, the public plan wins the game,” Nelson said. He called the inclusion of a public plan in legislation a “deal-breaker” for him.

Nelson’s opposition to a public plan is not unexpected. He has been widely considered the most conservative Democrat in the Senate — at least, until Pennsylvania’s Arlen Specter switched parties this week. And without Nelson’s support, Democratic leaders have little hope of garnering 60 votes for a health care overhaul, the number required to break a filibuster.

But they may not need to. The fiscal 2010 budget resolution (S Con Res 13) adopted Thursday would allow Democrats to pass a health care overhaul through the Senate with just 51 votes, using the procedure called reconciliation. Nelson voted against the budget, in part because of that provision.