An extensive Pentagon report about the armed forces' attitudes toward gays in the military gives a boost to the stalled push by President Obama to repeal the 17-year-old "don't ask, don't tell" law, undercutting arguments by Republicans and others that such a change would unduly strain the armed forces.

After nine months of study and unprecedented polling of the nation's troops, the Pentagon concluded Tuesday that allowing gays and lesbians to serve openly posed a "low risk" of disruption. The report found that a large majority of troops were comfortable with the prospect of overturning long-standing restrictions on gays in uniform and that they expected it would have little or no effect on their units.

"This can be done, and should be done, without posing a serious risk to military readiness," Defense Secretary Robert M. Gates said. He urged the Senate to pass legislation before it adjourns this month and a new Congress - in which the GOP will hold much more sway - is seated in January.

Senate Democrats are pressing to move fast and have scheduled hearings starting Thursday.

Majority Leader Harry M. Reid (D-Nev.) has vowed to hold a vote on the bill this month, but whether he'll be successful is an open question.

"The report is common sense," Reid said Tuesday. "It's no surprise to me. It's no surprise to the American people."

The bill's fate rests largely on the votes of about 10 moderate senators of both parties who are waiting to read the report before making their decision. Already Sens. Susan Collins (R-Maine), Richard G. Lugar (R-Ind.) and Lisa Murkowski (R-Alaska) have said they will vote to end the ban if Democrats permit a fair debate.

Sen. Ben Nelson (D-Neb.) said ending the ban "doesn't have to be done during the lame-duck session."

Obama also asked the Senate to vote soon, "so I can sign this repeal into law this year and ensure that Americans who are willing to risk their lives for their country are treated fairly and equally."

On Thursday, the Senate Armed Services Committee will question Gates; Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff; and the report's co-authors, Army Gen. Carter F. Ham and Pentagon counsel Jeh C. Johnson.

On Friday, the committee will ask the chiefs of staff of the Army, Navy and Air Force, as well as the commandants of the Coast Guard and Marine Corps, to express their personal views - which do not necessarily match up with the Obama administration's position. The panel's ranking Republican, Sen. John McCain (Ariz.), is a lead critic of efforts to repeal the ban. He did not comment Tuesday on the report.

Gates acknowledged Tuesday that military leaders of the individual branches of the armed services are "less sanguine" about the need to end the ban. The joint chiefs met with Obama at the White House on Monday to discuss the report. They have also written letters to Gates expressing their views on the study's findings. Pentagon officials declined to make the letters public.