Wal-Mart is the latest in a line of traditionally Republican-leaning businesses to embrace key portions of President Barack Obama's bid to overhaul health care, a trend that could complicate opponents' efforts to build a united front when Congress ramps up its work on the issue this summer.

Wal-Mart , the nation's largest private employer, on Tuesday endorsed the idea of requiring large companies to offer health insurance to their workers. The proposal is central to Obama's hopes of covering the nation's nearly 50 million uninsured and is disliked by some business groups.