The US Senate is to vote on the repeal of the "don't ask, don't tell" policy that prevents openly gay people serving in the military. Under the policy, which President Barack Obama has promised to scrap, gay people can serve but face expulsion if they reveal their sexuality. Opponents say repeal could lessen morale in the armed forces. On Monday, pop star Lady Gaga led a rally in Maine, where the two undecided senators may prove crucial to the vote. More than 2,000 people attended the rally at a park in Portland, where the singer stood alongside military veterans who were discharged from the US armed forces because of the policy. Wearing a jacket and tie, instead of one of her signature, flamboyant outfits, the singer suggested a new policy should target heterosexual soldiers who were "uncomfortable" with gay soldiers in their midst. A proposal to repeal the "don't ask, don't tell" policy is attached to a defence bill which the Democrats will try to bring to a vote this week. They need 60 Senate votes later on Tuesday to proceed to a debate on the bill. Senators Olympia Snow and Susan Collins, both of Maine, have yet to reveal their voting intentions and their votes may be necessary to avoid opponents using procedural delaying tactics. The Obama administration has said any repeal of the law would not be implemented until after the Pentagon completed a review of its impact on the armed forces. In the past, the issue of gay people in the military has divided opinion in the US. But most Americans now accept openly gay service personnel, according a recent Gallup poll. Credit: BBC