The US Defence Department has decided to allow women to serve aboard submarines. Defence Secretary Robert Gates has approved the recommendation and sent letters to Congress informing them of the plan. Congress now has 30 days to approve the measure. <br/><br/>The move comes as the US Army's chief of staff said it was time to revisit rules restricting women in combat roles. Fifteen per cent of the US Navy personnel are female, and women have worked alongside men on surface ships and aircraft since 1993.<br/><br/>