The senator asked Ballmer for details on the jobs to be eliminated; how many are held by H-1B or other work visa program employees; how many are held by Americans and, of those positions, how many similar positions held by foreign guest workers are being retained; and how many H-1B or other work visa program workers Microsoft will retain when the layoff is complete.

"My point is that during a layoff, companies should not be retaining H-1B or other work visa program employees over qualified American workers," Grassley wrote. "Our immigration policy is not intended to harm the American workforce. ... Microsoft has a moral obligation to protect these American workers by putting them first during these difficult economic times."

Grassley pointed out that Microsoft has lobbied Congress for an expansion of the H1-B program.

The program, as Grassley's office described it in a news release, "allows American companies and universities to employ temporary foreign guest workers who have the equivalent of a U.S. bachelor’s degree in a job category that is considered by the U.S. Citizenship & Immigration Services to be a 'specialty occupation.' The purpose of the H-1B program is to help companies hire foreign guest workers on a temporary basis when there is not a sufficient qualified American workforce to meet those needs."

A Microsoft spokeswoman told Reuters, that the company had not received the letter, but would respond to Grassley directly.

"I'm not aware of any rule that says you have to lay off H-1B workers before anyone else," said Cletus Weber, founder and partner with Mercer Island-based immigration law firm Peng & Weber. [Update, 4:45 p.m.: Weber did some additional research and added this via e-mail:

"I believe arbitrarily laying off lawfully employed foreign workers first would subject these companies to potential legal liability under federal anti-discrimination laws.

"Perhaps Senator Grassley forgot that Google and innumerable other large and small American companies that were founded by foreign workers have created tens of thousands of jobs for U.S. citizens. It is laudable for Senator Grassley to champion the cause of the American worker, but his calling for blatantly discriminatory layoffs is anti-competitive scapegoating, and in many ways removes some of the innovation that created large numbers of American jobs in the first place."]

In 2007, Microsoft said that about one-third of its 46,000 U.S.-based employees at the time had work visas or were legal permanent residents with green cards.

Update, 7:28 p.m.: Microsoft did respond to queries in the evening with this statement:

"We made the difficult decisions on which jobs would be eliminated based on a detailed assessment of our current and future business opportunities. The initial reductions we announced affect employees in a number of business units, and a significant number of the affected employees are foreign citizens working in this country on a visa. We recognize the human impact that our workforce reduction has on every affected worker and their families. For many of the employees here on a visa, being laid off means that they have to leave the country on very short notice, in many cases uprooting families and children. We care about all our employees, so we are providing services and support to try to help every affected worker, whether they are U.S. workers or foreign nationals working in this country on a visa."