In a big package of tax and spending legislation that Congress is likely to approve this week, Republicans have forced President Obama to swallow three changes that undermine his signature health care law, including a two-year delay of a tax on high-cost insurance plans provided by employers to workers.

In an interview on Wednesday, Mr. Obama’s first budget director, Peter R. Orszag, a leading supporter of the Cadillac tax, said, “The two-year delay is likely to be equivalent to repeal of the tax because people will expect it to be deferred again and again.”