WASHINGTON -- A Pentagon study on gays in the military has determined that overturning the law known as "don't ask, don't tell" might cause some disruption at first but would create no widespread or long-lasting problems. 

The study was expected to provide some needed ammunition to congressional Democrats struggling to overturn the law. Despite supporters' hopes to force a vote during the year-ending legislative session, it remains unclear whether the findings would be enough to sway skeptical Republicans, led by Sen. John McCain, a former Naval officer. 

Defense Secretary Robert Gates and the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, were expected to discuss the report later Tuesday, with the study's co-chairs, Pentagon General Counsel Jeh Johnson and Army Gen. Carter Ham. 

The findings were confirmed by several people familiar with the study who spoke on condition of anonymity because the results had not been released. 

The study found that 70 percent of troops surveyed believed that repealing the law would have mixed, positive or no effect, while 30 percent predicted negative consequences. Opposition was strongest among combat troops, with at least 40 percent saying it was a bad idea. That number climbed to 46 percent among Marines. 

The study also draws a strong correlation between troops who have worked with a gay service member and those who support repeal. According to the assessment, 92 percent of troops who have served with someone they believed to be gay thought that their unit's ability to work together was either very good, good or neither good nor poor. 

One person familiar with the report said it will show that military commanders believe gay and lesbian troops have a strong desire to fit in and feel accepted by their units. The report also will show that gay service members currently serving in the military have expressed a patriotic desire to serve and want to be subject to the same rules as other service members. 

The survey is based on responses by some 115,000 troops and 44,200 military spouses to more than a half-million questionnaires distributed last summer by an independent polling firm. 

The House of Representatives already has voted to overturn the law as part of a broader defense policy bill. Senate Republicans have blocked the measure in that chamber because they say not enough time has been allowed for debate on unrelated provisions in the bill. 

Senate Majority Leader Harry Reid has promised a vote on the matter by the end of the year, after hearings are held this week on the Pentagon study. Still, some gay rights groups have complained that Democratic leadership has done little to push for repeal before the new Congress takes over in January. 

Reid spokesman Jim Manley said the majority leader is "very much committed to doing away with the ban this year" but that any delay would be the Republicans' fault for blocking the bill.