For years, labor groups and others have blasted Wal-Mart for its stingy employee benefits, including making its low-income workers wait up to two years for costly insurance premiums.

But today, Wal-Mart President and CEO Mike Duke co-signed a letter — along with the heads of the Service Employees International Union and the Center for American Progress — supporting a proposal for a mandate on employers to provide insurance coverage for their workforces, the Associated Press reported.

In the letter [pdf] addressed to President Obama, Duke and the others ask for an employer mandate that is "fair and broad in its coverage."

Wal-Mart is the nation’s largest private employer, and SEIU — with more than 1 million members — has been a persistent critic. The retailer says 94 percent of its employees now are insured either by the company or a relative.

Here is an excerpt from the letter:

"We believe payment reform and efficiency initiatives need to be at the center of healthcare reform. The President and the Congress have put forward good ideas to improve the productivity of our health care sector. These policies need to be strengthened and adopted because health care reform without controlling costs is no reform at all.

"We are for shared responsibility. Not every business can make the same contribution, but everyone must make some contribution. We are for an employer mandate which is fair and broad in its coverage, but any alternative to an employer mandate should not create barriers to hiring entry level employees. We look forward to working with the Administration and Congress to develop a requirement that is both sensible and equitable."

According to AP, the letter "could give a push to two efforts: Wal-Mart's bid to improve its image regarding worker treatment, and Obama's plan to change the nation's health care system, including insuring virtually all Americans and controlling costs."