In theory, the furloughs that would be triggered by sequestration would be applied equally among all federal workers, but some are more equal than others.

Among the groups with a measure of protection from furloughs are some of the most senior presidentially appointed officials in the government, civilian employees in combat zones, foreign employees of the Defense Department and some workers involved in sensitive security issues.

The exemption for senior officials applies to all presidential appointees who are not governed by federal leave policies, according to the Office of Personnel Management.

“Leave-exempt Presidential appointees are not subject to furloughs because they are considered to be entitled to the pay of their offices solely by virtue of their status as an officer, rather than by virtue of the hours they work,” OPM spokesman Thomas Richards said by e-mail.

With hundreds of thousands of Defense federal employees facing the loss of up to 20 percent of their salaries in the event that there is no budget agreement to avert sequestration, the exemption for the highest-ranking officials is a sensitive matter for the federal government.

“It’s a little embarrassing, but it’s true,” said Robert F. Hale, comptroller for the Defense Department.

Deputy Defense Secretary Ashton Carter announced last week that he would return a portion of his salary to the federal government as a gesture of solidarity.

“I’m a presidentially appointed civilian and I can’t be furloughed, but I’m going to give back a fifth of my salary . . . at the end of the year, because we’re asking all those people who are furloughed to give back a fifth of their salary,” Carter told the House Armed Services Committee in testimony last week.

“I don’t think it’s right that they lose one-fifth of their paycheck and I don’t,” Carter said at a Senate Appropriations Committee hearing the next day.

His stance drew praise at the hearing from Sen. Lindsey O. Graham (R-S.C.), who suggested that he and his colleagues do the same.

“I think it would be very wise for us to follow your lead as members of the United States Senate, that if we can’t figure this out with the president, that all of us ought to follow your model, and for every day that sequestration’s in effect, the president should have his pay docked and we should have our pay docked, just to show that . . . we don’t live completely on a different planet, which some people think we do.”

Graham’s office said Friday that the senator will follow through on the suggestion. “He plans to and encourages other members of Congress and the President to do likewise,” spokesman Kevin Bishop said by e-mail.

The sequester would not affect lawmakers’ salaries, because their pay does not come from discretionary spending. However, the cuts would have an effect on their offices and staffs, as well as all legislative-branch agencies such as the Library of Congress, the Congressional Budget Office and the U.S. Capitol Police.

Whether that would include furloughs is up to individual lawmakers and agencies. The Government Accountability Office, for example, has told its workers that it does not expect any furloughs to be necessary, while the Library of Congress would consider four days of unpaid leave.

Such calculations are being made across the government. U.S. Customs and Border Protection has said it would furlough its employees for up to 14 days, and the Transportation Security Administration has said it would furlough its 50,000 officers for up to seven.

A petition on the White House Web site created Friday calls on the president and members of Congress to “share equally in the pain and suffering that they themselves are responsible for” and take a 20 percent cut.

In addition to Carter, two Pentagon officials — both members of the Senior Executive Service — have since said they would do the same, but have asked not to be identified, a Defense Department official said Thursday, adding that the issue is “super awkward.”

Officials at OPM and the Office of Management and Budget said they were unaware of any other senior government appointees who had offered to do so.

Although Pentagon officials have said that about 800,000 Defense civilian workers could be subject to furlough, about 50,000 of them are “foreign national” workers who are protected. They are employees at overseas bases including Germany, Afghanistan and Japan, assigned to duties that can include security, maintenance and food preparation.

The foreign workers’ employment is largely governed by status of forces agreements between the U.S. government and the host nation, and in some cases, particularly in Japan, the host nation pays their salaries.

Civilians working for the Defense Department in combat zones are exempted because of the critical nature of their work supporting troops.

The Pentagon also has made what Hale called “very limited exceptions” related to employees involved in the “protection of life and property” at Defense installations.

Josh Hicks contributed to this report.