A Pentagon study group has concluded that the military can lift the ban on gays serving openly in uniform with only minimal and isolated incidents of risk to the current war efforts, according to two people familiar with a draft of the report, which is due to President Obama on Dec. 1.

More than 70 percent of respondents to a survey sent to active-duty and reserve troops over the summer said the effect of repealing the "don't ask, don't tell" policy would be positive, mixed or nonexistent, said two sources familiar with the document. The survey results led the report's authors to conclude that objections to openly gay colleagues would drop once troops were able to live and serve alongside them.

One source, who has read the report in full, summarized its findings in a series of conversations this week. The source declined to state his position on whether to lift the ban, insisting it did not matter. He said he felt compelled to share the information out of concern that groups opposed to ending the ban would mischaracterize the findings. The long, detailed and nuanced report will almost certainly be used by opponents and supporters of repeal legislation to bolster their positions in what is likely to be a heated and partisan congressional debate.

President Obama has vowed to end the ban. Senior Pentagon officials requested the survey to address areas in which a repeal might cause conflicts that could hinder the military's ability to fight.

"There are challenges here, and we want the time so we can make the process of implementation as smooth as possible," said a second person who was briefed on the report but had not read it.

Defense Secretary Robert M. Gates, Joint Chiefs of Staff Chairman Mike Mullen, and uniformed and civilian leaders of the four military branches received copies of the draft report late last week.

The document totals about 370 pages and is divided into two sections. The first section explores whether repealing "don't ask, don't tell" would harm unit readiness or morale. It cites the findings of a survey sent over the summer to 400,000 active-duty and reserve troops, a separate questionnaire sent to about 150,000 military spouses, the responses submitted to an anonymous online drop box seeking comments, and responses from focus-group participants.

The second part of the report presents a plan for ending enforcement of the ban. It is not meant to serve as the military's official instruction manual on the issue but could be used if military leaders agreed, one of the sources said.

Among other questions, the survey asked if having an openly gay person in a unit would have an effect in an intense combat situation. Although a majority of respondents signaled no strong objections, a significant minority is opposed to serving alongside openly gay troops. About 40 percent of the Marine Corps is concerned about lifting the ban, according to one of the people familiar with the report.

A Defense Department spokesman declined to comment for this article.

House and Senate versions of the annual defense authorization bill include language that would repeal the ban, but it is not clear whether lawmakers will proceed with the measure during the lame-duck session slated to begin next week. At least 10 senators of both parties have said they will not decide how to vote until they read the final report.

In addition to political jockeying by groups for and against the ban, a Republican gay rights group has challenged the constitutionality of the policy in court. Its legal push led a federal judge to briefly block the military from enforcing the ban. In court papers filed Wednesday, the Justice Department said the Supreme Court should allow the Pentagon to continue enforcing it.