Democrats hailed the news Wednesday that Secretary of Defense Leon E. Panetta plans to lift the ban on women serving in combat.

A formal announcement is expected Thursday from the Pentagon, according to a senior defense official.

Carl Levin, D-Mich., chairman of the Senate Armed Services Committee, issued a concise written statement: “I support it. It reflects the reality of 21st-century military operations.”

Sen. Kirsten Gillibrand, R-N.Y., a member of the Armed Services Committee, also was effusive, noting that she helped insert language into the fiscal 2013 defense authorization law (PL 112-239) requiring a feasibility study on lifting the ban.

“This is a proud day for our country and the step we need to formally recognize the brave women who are already fighting and dying for our country shoulder-to-shoulder with their brothers in uniform on the frontlines,” she said in a written statement. “This decision finally opens the door for more qualified women to excel in our military and advance their careers, and obtain all of the benefits they have earned.”

A senior defense official explained that the policy change “will initiate a process whereby the services will develop plans to implement this decision, which was made by the secretary of Defense upon the recommendation of the Joint Chiefs of Staff.” The news was reported first by the Associated Press.

House Democrats also praised the decision by Panetta, who is expected to step down once the Senate confirms his successor, former Republican Sen. Chuck Hagel.

“I have been a firm believer in removing the archaic combat exclusion policy for many years,” Loretta Sanchez, D-Calif., a senior member of the House Armed Services panel, said. “I am happy to hear the secretary will be making significant changes as part of an effort to expand opportunities for women in the military.”

Congress ordered a review of women’s roles in combat in the fiscal 2011 defense authorization bill (PL 111-383), which followed a 2011 Military Leadership Diversity Commission report that recommended lifting all combat restrictions on women. The diversity commission was created as part of the fiscal 2009 defense authorization law (PL 110-417).

The chairman of the House Armed Services Committee suggested Wednesday that he might support the change.

“After a decade of critical military service in hostile environments, women have demonstrated a wide range of capabilities in combat operations and we welcome this review,” Rep. Howard “Buck” McKeon, R-Calif., said in a written statement.

Several Republicans, including the top member on the Senate Armed Services panel , James M. Inhofe, were angry that Congress was not briefed before the move was reported in the press.

“It is unacceptable that information on the Defense Department’s plans related to women in combat was leaked prior to Congress being briefed,” Inhofe said in a written statement Wednesday. “I do not believe this will be a broad opening of combat roles for women, because as the 2012 report indicated, there are ‘serious practical barriers which must be resolved so that the department can maximize the safety and privacy of all military members while maintaining military readiness.’”

Inhofe said he has supported previous expansions of women’s roles in the military, but several Republicans have voiced broader opposition to suggestions about relaxing the ban in the past.

“It’s a proposal that could seriously harm both the morale and the on-the-ground capabilities of our military,” Rep. Trent Franks, R-Ariz., a member of the House Armed Services Committee, wrote in 2011 in CQ. “As much as some feminists may begrudge biology for undermining their arguments, the fact remains that men and women are different.”

Sen. Jeff Sessions, a senior member of the Senate Armed Services Committee, said he had not received advance word of Panetta’s move.

“That is a decision one would expect the Pentagon to consult with congress about,” he said Wednesday.

But perceptions of women in combat roles have undergone a significant shift since the 1991 Persian Gulf War, in which some women played important roles. A more radical shift occurred during the past 10 years, as the wars in Iraq and Afghanistan created muddled battle lines that often left women in direct combat.

Several female members of Congress have been deployed to combat zones, including freshman Rep. Tulsi Gabbard, D-Hawaii, who served two tours in the Middle East.

“Female service members have contributed on the battlefield as far back as the Civil War, when some disguised themselves as men just to have the opportunity to serve their nation,” Gabbard said in a statement Wednesday. “This decision by the Department of Defense is an overdue, yet welcome change, which I strongly support.”

According to the Congressional Research Services, over the years, more than 283,000 female servicemembers have been deployed worldwide.

“In approximately 10 years of combat operations in Iraq and Afghanistan, over 800 women have been wounded and over 130 have died,” CRS stated in a December report. “According to the Department of Defense (DOD), as of February 29, 2012, over 20,000 female members have served or are serving Afghanistan and Iraq. (U.S. forces were out of Iraq as of Dec. 2011).”

Indeed, two women have received the Silver Star, the second highest award for valor.

Primarily, women are barred from infantry, artillery, armor, combat engineers, and special operations units of battalion size or smaller. But the restrictions on their roles are a matter of policy that the administration and the Pentagon may modify, according to CRS.

In 2010, the Navy notified Congress that it was modifying its policy to allow women to serve as permanent crew members aboard submarines. More recently, Army doctrine changes “called into question the ground exclusion policy, or at least, the services’ adherence to it,” CRS stated. “This is the result particularly from the policy of collocating support units (to which women are assigned) with combat units, along with adapting to the unusual (nonlinear) warfare tactics encountered in Iraq and Afghanistan, and the utilization of women in what some view as new nontraditional roles in Iraq and Afghanistan.”